The Great Wall___ all over the world.
A. knows
B. knew
C. was known
D. is known
It's common knowledge that black tea_____in China more than 600 years ago.
A. is invented
B. was invented
C. invents
D. invent
Do you like the material? yes. it ___ very soft.
A. is feeling
B. felt
C. feels
D. is felt
Waste paper shouldn' t _______ everywhere. It's our duty to keep our city clean.
A. be thrown
B. throw
C. is thrown
D. are thrown
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