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- _____ you _____ your homework yet?—Yes, I _____ it ten minutes ago.
- ________you _____your homework yet? —Yes, I ___it ten minutes ago.
- Why haven’t you asked her to come here?—She _______ an important experiment when I found her and she _____ it.
- So far we have done a lot to build a low-carbon economy, yet it is still _________ ideal. We have to work even harder.