Problem: Extract the answer to the question from the following context. Question: What happened second, the first traffic light exploded or the first modern electric traffic lights were put up? Context: Green can communicate safety to proceed, as in traffic lights. Green and red were standardized as the colors of international railroad signals in the 19th century. The first traffic light, using green and red gas lamps, was erected in 1868 in front of the Houses of Parliament in London. It exploded the following year, injuring the policeman who operated it. In 1912, the first modern electric traffic lights were put up in Salt Lake City, Utah. Red was chosen largely because of its high visibility, and its association with danger, while green was chosen largely because it could not be mistaken for red. Today green lights universally signal that a system is turned on and working as it should. In many video games, green signifies both health and completed objectives, opposite red.

A: the first modern electric traffic lights were put up

Problem: Extract the answer to the question from the following context. Question: what was the last word in the passage? Context: A wide range of beliefs and practices is found across the world among those who call themselves Christian. Denominations and sects disagree on a common definition of "Christianity". For example, Timothy Beal notes the disparity of beliefs among those who identify as Christians in the United States as follows:

A: follows

Problem: Extract the answer to the question from the following context. Question: Which of the following is not a possible meaning of aktualny: present, timely or ecological? Context: Generally, the greater the contact and exchange that have existed between two languages, or between those languages and a third one, the greater is the ratio of metaphrase to paraphrase that may be used in translating among them. However, due to shifts in ecological niches of words, a common etymology is sometimes misleading as a guide to current meaning in one or the other language. For example, the English actual should not be confused with the cognate French actuel ("present", "current"), the Polish aktualny ("present", "current," "topical," "timely," "feasible"), the Swedish aktuell ("topical", "presently of importance"), the Russian ("urgent", "topical") or the Dutch actueel.

A: ecological

Problem: Extract the answer to the question from the following context. Question: The visuals are created through? Context: The structure of QD-LEDs used for the electrical-excitation scheme is similar to basic design of OLEDs. A layer of quantum dots is sandwiched between layers of electron-transporting and hole-transporting materials. An applied electric field causes electrons and holes to move into the quantum dot layer and recombine forming an exciton that excites a QD. This scheme is commonly studied for quantum dot display. The tunability of emission wavelengths and narrow bandwidth is also beneficial as excitation sources for fluorescence imaging. Fluorescence near-field scanning optical microscopy (NSOM) utilizing an integrated QD-LED has been demonstrated.

A:
imaging