选择方框内所给词的适当形式填空。（注意词形变化）。（每空一词）

leave,  work,  park,  phone,  own

How do you study for a test? By _______ with a group.
Teenagers should be allowed to choose their _____ clothes.
What will you do in your free time? I’ll help to clean up the city _____.
Do you know when the _____ was invented? It was invented in 1876.
By the time I got outside, the bus had already _____.