There are so many books! It is not easy for us to decide what to take and what to_______.
It was not until 1911, _______ the first vitamin was identified, _______ people realized the importance of it.
The moment I completed the 800-meter race in the school sports meet, my legs _______.
We’ve just heard a warning on the radio _______ a typhoon may be on its way.
Traditional Chinese medicine is thousands of years old and has developed _______ time.
_______ with the Japanese government, some Chinese people decided not to buy products from Japan any more.