1 .          , you can turn to me for help.

A．However the problem is difficult	B．No matter how difficult is the problem
C．No matter how is difficult the problem	D．However difficult the problem is

2 . ______ I agree with you, I don’t think your solution is the best.

A．If

B．Since

C．While

D．As

3 . ________in everyday life consumers have seen lots of successful examples of advertisements like Kodak, Nike, Coca-Cola, and McDonald’s, there are still some examples that do not reach the expected goal.

A．As

B．Because

C．In addition

D．While

4 . ________ everyone has left the party, we need to start cleaning.

A．Before

B．Whenever

C．Now that

D．In case