Experiments of this kind _______in both the U.S. and Europe well before the Second World War started.

 I_____ violin lessons every two weeks, but I think I will make it every week from next month.

Having you ever ______ in front of thousands of people at a concert, with everyone _____ while you were singing?

 ---How much is the petrolper liter today? ---Oh, 6.00 yuan. It ______ sharply since last month.

一"Peter, have you got your new flat furnished?—Yes. I ______ some used furniture and it was a real bargain.