The threats to the health of astronauts in space are very different from __________ on earth.
____ Chinese are learning English for a better future.
The box was too heavy for me to carry, ___ I pulled it into my room.
Sam enjoys ___ stamps.
___ many children like sugar, I think they had better try not to eat it too often.
—What are you doing?—I’m ___ my cat. I can’t find it.