The Chinese abacus(算盘), officially ______ as a cultural heritage at the 8th Annual UNESCO World Heritage Congress, is another symbol of Chinese wisdom.
At the school gate, you should _____ the safeguard with your student card.
Father insisted Tom _____ all his homework before he went to bed.
I met this guy _____ some other occasions but he did not seem to recognize me.
I don’t like the lecture yesterday. Most of what the speaker said was _____ the subject.
The demand for _____ skilled workers is still increasing.