Exploring _____space is exciting, yet dangerous. There is _____need for both robots and humans for space exploration.
English is a language shared by several different cultures, but each of ______ uses it somewhat differently.
Have you ever had the case _______ you can’t recognize your friend’s voice on the phone?
He made another wonderful discovery,_____ of great importance to science.
When the poor old lady tried to ______ the cup on the shelf to have a drink, she ______.
Maria has written two novels, both of _____ have been made into television series.