That was the fourth time that Mr. Smith __________the Summer Palace.

is more important isas the earth cooled down, water began to appear on its surface

I really apologize for not being able to join in your birthday party. –________. We’ll get together later.

When _______, the new stadium（体育馆） will hold 50000 people.

Most middle schools prefer to buy _______ desks, so they can change to suit students’ growing height.