While other scientists are keeping____eye on changes in the H5N1 bird flu strain, the scientists in England are working on vaccines, in case it becomes highly infectious in ____humans.
| A．a , / | B．an, / | C．the, an | D．an, the |
Giving small children some money as a gift during the Spring Festival is a common ______ in China, which may seem strange to foreigners?
| A．sense | B．practice | C．ground | D．habit |
__ recent report stated that the number of Spanish speakers in the US would be higher than the number of English speakers by __ year 2090.
| A．A, the | B．A, / | C．The , / | D．The, a |
If you go by __ train, you can have a comfortable journey, but make sure you get __ fast one.
| A．the , the | B．/, a | C．the , a | D．/, / |
It is often said that __ teachers have __ very easy life.
| A．/, / | B．/, a | C．the, / | D．the, a |
I can’t remember when exactly the Robinson left __ city. I only remember it was __ Monday.
| A．the, the | B．a, the | C．a, a | D．the, a |