Peter was so excited ______ he received an invitation from his friend to attend the wedding.

When you read a book, you should make a mark ______ you have any question.

He is rather difficult to make friends with, but his friendship, _____ is more true than anyone else’s.

He tried his best to solve the problem, _______difficult it was.

—Will the match be cancelled because of the bad weather?
—No, rain or shine, the match will be held as     .

________, it began to rain unexpectedly.

_____by a greater demand for vegetables, farmers have built more green houses.

You shouldn’t keep silent when ____

Come and see me whenever ________.

Diaoyu Island issue, unless ________ properly, will directly affect smooth development of relationships between China and Japan.