New drugs or devices must be tested before being

For data transmission to be successful，sending and receiving devices must follow a set of

About half an hour before the engine is required, cooling water at _____ must be circulate

Immigrants to the UK are being tested on their English skills before being able to claim i

The electric shaver______before it can be used.A．must repairB．should be in repairC．has to

Some people are accustomed to thinking that facts must either be believed or they must be

People can be addicted to different things—e.g. alcohol drugs certain foods or even te