①一立方英寸被压扁的沙子比一立方英寸普通的沙子要重得多。____
②因此,目前存在两种对立的理论,即“撞击说”和“火山说”。____
The floor is very dirty. Will you please ______?
Information about a trip
Where to go
________
How to go there
How far
What to visit after lunch
When to come back