It's the second time that I ________ to Shanghai．It's ten years since I ________ it last time．

A．have been；left         B．had been；left       C．am；had left            D．come；had left

The message is very important，so it is supposed ________ as soon as possible．

A．to be sent             B．to send          C．being sent               D．sending

Einstein like Bose's paper so much that he ________ his own work and translated it into German．

A．gave off          B．turned down          C．took over                  D．set aside

I like getting up very early in summer．The morning air is so good ________．

A．to be breathed           B．to breathe           C．breathing             D．being breathed

The country has already sent up three unmanned spacecraft，the most recent ________ at the end of last March．

A．has been launched                             B．having been launched

C．being launched                                    D．to be launched

At the beginning of class，the noise of desks ________ could be heard outside the classroom．

A．opened and closed                                   B．to be opened and closed

C．being opened and closed                           D．to open and close

The steam engine gives us an example of heat ________ into work．

A．turns            B．turned            C．turning                 D．being turned

It is strongly recommended that the machine ________ until it has been fully checked．

A．is not used                                                B．will not be used

C．not be used                                               D．is not to be used

My morning ________ includes jogging in the park and reading newspapers over breakfast．

A．drill          B．action             C．regulation               D．routine

Some blood types are quite common，others are regionally ________，and still others are rare everywhere．

A．distributed            B．contributed           C．obtained            D．contradicted