1.__was a photo.A.Enclosed in the letter B.In thhe letter en

1.__was a photo.A.Enclosed in the letter B.In thhe letter enclosed C.The letter enclosed in D.In enclosed the letter这个题怎么选?为什么?
2.The pressure__causes Americans to be energetic,but it also puts them under a constant emotional strain.A.to compete B.competing C.to be competed D.having competed为什么不选B而是A
3.He will agree to do what you require__him.A.of B.from C.to D.for为什么选A,也没有require of sb.的搭配呀,为什么不是D?