He switched off the light and was about to leave the classroom and only then ________ to rain heavily.
When you write to him, please _____ him.
-- Tom works hard at English.?-- _____, and _____.
After he gave a report about the school, Mr White____ the visitors around it.
It is believed that ______ European chemist called Felix Hoffmann first produced ASA which completely changed ______ man’s understanding of aspirin.
At the United Nations Climate Change Conference, the UN Secretary General points out that, ______, the climate situation will get worse and worse.