공부하다가 모르는게 있어서 질문합니다.

아시는 분은 답변좀해주세욤

1.

A large percentage of students admitted to the premier MBA programs have undergrauate degress in economics.

A large percentage에서 A는 왜 붙었나요?

2.

Mr. Eisenhower was offered a number of positions in the company, none of which was exactly what he was looking for.

none 이하 문장이 이해가 안되네요-_-;;

여기서 which랑 what은 뭘로 쓰엿나요?

3.

It is the company's policy that the director himself must abstain from any political involvement in carrying out his reponsibilities.

여기서 that이하 문장과 company's policy가 동격인가요?

4.

Top Travel is the number one agency in the country because it offers many excitement package tours for its clients to choose from.

to choose from은 왜 쓰엿나요? 그리고 무슨 뜻인가요>?