Some researchers believe that the Philippines' complete reliance on security provided by the United States in the context of the Asian Cold War is a profound reason why it cannot refuse the United States to require it to send troops to Vietnam; while avoiding direct involvement in the Vietnam War, which is not very relevant to its own interests and has serious risks, is The Philippines has chosen to send only a small number of civilian engineering troops, but has always refused the deep motivation of sending combat troops. Which of the following, if true, can refute the above statement? ['Philippines sends troops to the United States on condition that the United States provide them with security.', 'Philippines sends engineering troops to Vietnam, indicating weak alliance with the United States.', 'Philippines sending combat troops to Vietnam could pose serious risks to itself.', 'Philippines does not reject U. S. troop request because the economy is heavily dependent on the U. S.']