题目
Complete the sentences with the words given below.-|||-what that which when whether-|||-1 It is certain __ they will be able to arrive here on time.-|||-2 __ is discussed at the meeting must be kept secret.-|||-3 __ the pyramids were built is still unknown to us.-|||-4 It is not clear __ the conference will be postponed (推迟)-|||-5 __ will be the best solution is our biggest concern.

题目解答
答案
1.that
2.What
3.When
4.whether
5.What