Astronomers and scientists think that a black hole is a region of space ______ which matter has fallen and _______ which nothing can escape.
When the market economy is introduced, many factories will not .
“___________ the election is over,” said Powell, “the time has come for me to step down as secretary of state and return to private life.”
—Having many helpers makes a task easier and faster to complete. —I think so. _______ .
The teacher suggested the dictionary at once.
______ the prices of color TV sets down by 50%, the company had a very hard time.