Question: Jonas Černius was appointed to be Prime Minister of Lithuania by an official in which government office?

Context paragraphs:
Prime Minister of Northern Ireland: The Prime Minister of Northern Ireland was the head of the Government of Northern Ireland between 1921 and 1972.  No such office was provided for in the Government of Ireland Act 1920, however the Lord Lieutenant, as with Governors-General in other Westminster Systems such as in Canada, chose to appoint someone to head the executive even though no such post existed in statute law.  The office-holder assumed the title "Prime Minister" to draw parallels with the Prime Minister of the United Kingdom.  On the advice of the new Prime Minister, the Lord Lieutenant then created the "Department of the Prime Minister".  The office of Prime Minister of Northern Ireland was abolished in 1972, along with the contemporary government, when direct rule of Northern Ireland was transferred to London.

Office of the Prime Minister (Canada): In Canada, the Office of the Prime Minister (more commonly referred to as the Prime Minister's Office and abbreviated as PMO), located in the Office of the Prime Minister and Privy Council, facing Parliament Hill, in Ottawa, is one of the most powerful parts of the government.  It is made up of the prime minister and his or her top political staff, who are charged with advising the prime minister on decisions, making the office a wholly partisan body.  It should not be confused with the Privy Council Office (PCO), which is the top office that controls the civil service and is expressly non-partisan.  The PMO is concerned with making policy whereas the PCO is concerned with executing the policy decisions decided by the government.

Swedish governmental line of succession: The Swedish constitution of 1974 allows the Prime Minister of Sweden to appoint one of the Ministers in the cabinet as Deputy Prime Minister ("biträdande statsminister", also unofficially known as "vice statsminister", "Vice Prime Minister"), in case the Prime Minister for some reason is prevented from performing his or her duties.  However, if a Deputy Prime Minister has not been appointed, the Minister in the cabinet who has served the longest time (and if there are several with equal experience the one who is oldest) takes over as head of government.  Note that the person acting as Prime Minister does not do so on a permanent basis: if a Prime Minister dies, resigns or loses a vote of confidence in the Riksdag, the Speaker of the Riksdag will then confer with the parties of the Riksdag and propose a new Prime Minister, who must be tolerated by a majority of the Riksdag.  If the Prime Minister has resigned or lost a vote of confidence, he or she will remain the head of a government "ad interim" until the new Prime Minister assumes his or her office.  The only case where the governmental line of succession becomes relevant is when the Prime Minister dies (upon which the person next in the line of succession serves as the head of a government "ad interim") or when the Prime Minister is on leave or for any other reason incapable of serving, but still remains in office.  This might be compared to the Presidential line of succession in the United States, where the person next in line assumes the Presidency throughout the remainder of the term if the President dies, resigns or is impeached.

Prime Minister of Armenia: The Prime Minister of Armenia is the head of government and most senior minister within the Armenian government, and is required by the constitution to "oversee the Government's regular activities and coordinate the work of the Ministers."  The Prime Minister is appointed by the President of Armenia, but can be removed by a vote of no confidence in Parliament.  The office of President is generally considered to be more powerful than the office of Prime Minister.  In constitutional referendum held in 2015, citizens voted in favor of transferring Armenia into a parliamentary republic.  It will be fully introduced in 2018.  The office of President will become ceremonial post and Prime Minister's office will be the most powerful in the country.

Jonas Černius: Jonas Černius (6 January 1898, Kupiškis, Kovno Governorate – 3 July 1977, Los Angeles) was a Lithuanian general and Prime Minister.  When Lithuania declared independence in 1918, he joined the army as a volunteer and participated in the Freedom Wars.  He was one of the first graduates from the War School of Kaunas, but he continued to study military engineering in Brussels (1929) and Paris (1932).

Abd Allah Siraj: ‘Abd Allāh ibn ‘Abd ar-Raḥman Sirāj (Arabic: عبد الله بن عبد الرحمن سراج‎ ‎ ) was an Arab politician and Islamic scholar who held various posts in the Kingdom of Hejaz and later the Emirate of Transjordan, including the office of Prime Minister of both countries.  Born in Mecca, he graduated from Madrasah as-Sawlatiyah and later al-Azhar University in Cairo.  In 1907 he was appointed Mufti of the Hanafis in Mecca by Sharif Ali Abd Allah.  He was elected to represent Mecca in the Ottoman parliament in 1908, though he resigned before he ever served.  After Sharif Husayn declared independence from the Ottoman Empire in 1916, he appointed Siraj as Chief Justice and Deputy Prime Minister of the Hejaz government.  Siraj served as acting Prime Minister in lieu of Emir Ali until 1918.  After Husayn abdicated the throne in 1924, Siraj held the office of Prime Minister during most of Ali's short reign, which ended with the Kingdom's surrender to the Saudi Sultanate of Nejd in 1925.  He then migrated to the Jordan, where under Emir Abd Allah he served as Prime Minister from 1931 to 1933 while simultaneously holding the portfolios of Finance and the Interior Ministry, as well as the office of Chief Justice.

Prime Minister of Lithuania: The Prime Minister of Lithuania (Lithuanian: "Ministras Pirmininkas" , literally translated as Minister-Chairman) is the head of the Government of Lithuania, and is appointed by the President of Lithuania with the assent of the Lithuanian parliament, the Seimas.  The modern office of Prime Minister was established in 1990, during the turmoil surrounding the Soviet Union's collapse, although the official title was "Chairperson of the Council of Ministers" until 25 November 1992.

Government Office for Science: The Government Office for Science is part of the British government.  This organisation advises the UK Government on policy and decision-making based on robust scientific evidence and long-term thinking.  It is led by the Government Chief Scientific Adviser (GCSA), Sir Mark Walport who reports to the Prime Minister and Cabinet.

Henry John Temple, 3rd Viscount Palmerston: Henry John Temple, 3rd Viscount Palmerston, (20 October 1784 – 18 October 1865), was a British statesman who served twice as Prime Minister in the mid-19th century.  For most of 1830 to 1865 he dominated British foreign policy when Britain was at the height of its power.  Popularly nicknamed "Pam" and "The Mongoose", he was in government office almost continuously from 1807 until his death in 1865, beginning his parliamentary career as a Tory, switching to the Whigs in 1830, and concluding it as the first Prime Minister of the newly formed Liberal Party from 1859.

Cabinet of Malaysia: The Cabinet of Malaysia is the executive branch of Malaysia's government.  Led by the Prime Minister, the cabinet is a council of ministers who are accountable collectively to the Parliament.  According to the Article 43 of the Constitution, members of the Cabinet can only be selected from members of either houses of Parliament.  Formally, the Yang di-Pertuan Agong appoints all Ministers on the advice of the Prime Minister.  The constitution is amended by repealing the Clause (8) of Article 43, enabling a person who is a member of State Legislative Assembly to continue to be one even when he or she is appointed as a minister or deputy minister in the cabinet.  Ministers other than the Prime Minister shall hold office during the pleasure of the Yang di-Pertuan Agong, unless the appointment of any Minister shall have been revoked by the Yang di-Pertuan Agong on the advice of the Prime Minister but any Minister may resign his office.  In practice, the Yang di-Pertuan Agong is obliged to follow the advice of the Prime Minister on the appointment and dismissal of ministers.

Supporting paragraphs: Jonas Černius Prime Minister of Lithuania
Answer: the President of Lithuania