Yang Liwei showed the flags of China and the United Nations, ________ the wishes of Chinese people to use space peacefully.

When will you come to see me, on Tuesday or Thursday—__________ day is OK. I’m on holiday.

It is difficult for us to _________ a conversation with so much noise around us.

Most of the professors _____ to our schoolwere from South Africa．

____ he will come or not is still unknown