I didn’t quite follow him because he explained the theory _____that is too abstract for me.
It is amazing that the little boy can swim ______the river ______100 meters wide.
In order to meet the deadline, Professor Smith along with his assistants the project day and night.
Although dragon doesn’t exist, we still take it as a _______ of our nation.
Baseball requires teamwork _______ tennis is an individual sport.
--- The earthquake last night was really terrible. --- ______, no people were injured or killed, and they escaped in time.