It is often necessary to put an engine into ____ service with once or more cylinders cut out under emergency condition.

单选题

It is often more difficult to find trained men than ___for scientific research.

答案解析

单选题

— What’s the weather often like in our home town in early spring? ―There is much ______ here and It’s often ______.

答案解析

单选题

It is showed in a(n)（____）that people often read what other people post on social media.

答案解析

单选题

It is often necessary to put an engine into ____ service with once or more cylinders cut out under emergency condition.

答案解析

单选题

The procedures should address how often the program will be reviewed to determine if it is current and adequate for the type of maintenance being performed at the facility.

答案解析