Earth is believed ______ by an object the size of Mars at some point in the distant past before its surface cooled.
We have worked out the plan and now we must put it into ________.
Anyway,I can’t cheat him—it’s against all my________. (2011·浙江,18)
Teachers have to constantly update their knowledge in order to maintain their professional________. (2011·江苏,27)
There’s a ________ in our office that when it’s somebody’s birthday,they bring in a cake for us all to share. (2011·山东,34)
Always remember to put such dangerous things as knives out of children’s ________. (2011·四川,13)