Why was waging war in vietnam difficult for US soldier

This term, coined by john o’sullivan in 1939, represented the belief that god had preordained the u.s. to settle the whole continent and spread its influence and culture there a.) women’s suffrage b.) the industrial age c.) manifest destiny d.) the abolition movement

Which historical interpretation is supported by this source?

Can someone answer these question about vasco de gama for me: when? (when did he started his travel)from where & to where? (from where he was and then where he went to)motives? (what was his motives for traveling)accomplishments & discoveries? i will give you 15 star for answering all of these, you so much.