用括号内所给动词的适当形式填空。
The garden is the best place ____ (grow) flowers.
This pair of jeans ____  (match) his white shirt.
Listen! How wonderful the music____ (sound) ！
 Mary, ____  (not be) afraid of the dog. It never bites.
 Keep quiet, the students ____ (prepare) for the coming exam.
____  (ride) a bike to school is good for your health.
Sandy spends a lot of time____  (chat) with her e-friend on the Internet.
How long does it take you____ (walk) to school every day?
I don’t have any ideas, I don’t know where ____ (go).
Would you like____ (drink) a cup of tea?

某种商品经过两次降价，由每件100元调至81元，则平均每次降价的百分率是（   ）