The work he devoted his time to _____ worth praising.
Special attention should be paid _______ our earth from _______.
The roof fell _______ he had time to dash into the room to save his baby.
Rock climbing is _______ great fun. You will get close to _______ nature and take adventures at the same time.
When the teacher came in, the students pretended _____ the text.
In order to continue to learn by ourselves when we have left school, we must ______ learn how to study in the school now.