It took years for Einstein"s theor

1、For many years, people electric cars.

For many years, people electric cars. However, making them has been more difficult than predicted.Ahad dreamed ofBhave dreamed ofCdreamed ofDdream of

2、For some years after his graduation, h

For some years after his graduation, he（）some of his classmates, but as times went by, he dropped them one by oneAcaught up withBkept in touch withCkept upDmade up with

3、Radio communication（）for many years an

Radio communication（）for many years and helps to save tens of thousands of lives.Ahas been usedBhave been usedChas usedDhave used

4、It took me a long time before I was ab

It took me a long time before I was able to fully appreciate what they __ for me.A had doneB didC would doD were doing

5、It（）exactly thirty years since I gradu

It（）exactly thirty years since I graduated from college.AwasBhas beenCwas beDhad bee

6、It took us quite a long time to get to

It took us quite a long time to get to the amusement park. It was journey.A three hourB a three-hoursC a three-hourD three hours