. —Which is _______, the sun, the earth or the moon —Of course, the sun.

he summer vacation, the professor, together with his fellow teachers, ______ thescientific experiment

We would appreciate _______ if you could give us some advice on how to solve this problem.

near future, more advances in cloningtechnology by scientists

It’s December now. In _____ three weeks, we’ll have our winter holiday.