He began exploring North America in 1603
B. Sea life. This is because all of the other three options are very publicized, but sea life is not.
I am not going to answer in a paragraph of 125 words, but I will give you the answer to the first question; The United States didn't want another country to fall to communism. They officially got involved after the attack of the Gulf of Tonkin (U.S destroyers were stationed there and a radio came in that said they had been fired upon by North Vietnamese forces). (45 words BTW).