帮我解决下列英语问题（最好有详细解释）
1.For the success of the project ,the company should__the most of the opportunities at hand.
A.obtain B.grasp C.catch D.make （答案选D,为何不选B）
2.He began by making a few general observations__the report.
A.towards B.about C.of D.with(答案选B为何不选C)
3.The chairman of the company said that new techniques had__improved their production efficiency.
A.violently B.severely C.extremely D.radically（答案选D,为何不选C）
4.__mainly for the invention of the telephone,Alexander Graham Bell devoted his life to helping the deaf.为何不选A）
A.Though remembered B.While remembering
5.It is imprpbable that he will ever again in his life__so much without having to do anything in return.
A.give B.to give C.be given D.to be given(答案选C)
6.He should__ his own living.
A.operate B.manage C.handle D.earn(答案选D,为何不选B)