同步发电机并联合闸时，实际中通常使发电机频率略高于电网频率，为什么？

Lewis had to travel by bus (as) his car (had been damaged) in an accident some days (before) and he (was failed) to get it repaired.

A．as

B．had been damaged

C．before

D．was failed

Lewis (had to) travel (by bus) as his car (had been damaged) in an accident some days before and he (was failed) to get it repaired.

A．had to

B．by bus

C．had been damaged

D．was failed

People didn't wash in those days because ______.

A．they had no water in their houses

B．they had to buy water from a water-carrier and it was expensive

C．soap was expensive, too

D．all of the above

We haven’t had any customers visiting restaurant for days, there must be something () the dishes we serve.

A.good at

B.rotten

C.wrong with

D.bad with

We had a marvelous holiday. only the last two days were slightly ______ by weather.

A．damaged

B．enhanced

C．spoiled

D．diminished

We had a marvelous holiday. Only the last two days were slightly ______ by weather.

A．damaged

B．enhanced

C．spoiled

D．diminished

Lewis had to travel by bus(as )his car (had been damaged )in an

A B

accident some days (before )and he (was failed )to get it repaired.

C D

We had a marvelous holiday; only the last two days were slightly ______ by weather.

A．damaged

B．enhanced

C．spoiled

D．diminished

We had a marvelous holiday. Only the last two days were slightly________by weather.

A．damaged

B．enhanced

C．spoiled

D．diminished

Your letters ______ those pleasant days when we worked together, I'll remember forever.

A．call out

B．call for

C．call up

D．call on