选出对句子画线部分结构描述正确的选项

The research is so designed that once begun nothing can be done to change it．

宾语

定语

状语

选出对句子画线部分结构描述正确的选项

Unless invited to speak, you should remain silent at the conference．

宾语

表语

状语

I’ve tried very hard to improve my English．But by no means ________ with my progress．

the teacher is not satisfied

is the teacher not satisfied

the teacher is satisfied

is the teacher satisfied

I have to go to work by taxi because my car ________ at the garage．

will be repaired

is repaired

is being repaired

has been repaired

Although the causes of cancer ________, we do not yet have any practical way to prevent it．

are being uncovered

have been uncovering

are uncovering

have uncovered

I won’t tell the student the answer to the math problem until he ________ on it for more than an hour．

has been working

will have worked

will have been working

had worked

This machine ________．It hasn’t worked for years．

didn’t work

wasn’t working

doesn’t work

isn’t working

As you can see, the number of cars on roads ________ rising these days．

was keeping

keep

keeps

were keeping

Professor Smith, along with his assistants, ________ on the project day and night to meet the deadline．

work

working

is working

are working

Ladies and gentlemen, please fasten your seat belts．The plane ________．

takes off

is taking off

has taken off

took off