I can never forget the days _____ we worked together and the days _____ we spent together.A. when; which B. which; when C. what; that D when; when
– Let’s go skating, shall we? --That’s not a good idea; the ice is too thin _____ your weight.
–Where do these books _____? --Put them back _____they were.
After a long time for many years, he is now _____.
–Don’t you think it a very nice motorbike? --Yes, but would you please ____ it on my lawn?
-- _____is that used for? ---_____ the floor.