Studies have shown that scientists produce not only some of the best ideas, but also _____ bad ones.
–Have you ______? --Yes. Let me take you to a place to celebrate.
– 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?