——____ he start at once or wait for a while?——Let him start at once.
It is generally believed that reading is_________ it is a science.
It's always difficult being in a foreign country, _____if you don't speak the language.
_______to take this adventure course will certainly learn a lot of useful skills.
We decided not to climb the mountains because it was raining________.
The pianos in the other shop will be ________, but ________.