A lot of banks are ________ to the new electronic system because it's more efficient.
| A．switching on | B．switching off |
| C．switching over | D．switching from |
When you are home, give a call to let me know you __________ safely.
| A．are arriving | B．have arrived |
| C．had arrived | D．will arrive |
Tom __________ in the library every night over the last three months.
| A．works | B．worked |
| C．has been working | D．had been working |
—I remember you were a talented pianist at college. Can you play the piano for me?
—Sorry, I __________ the piano for years.
| A．don't play | B．wasn't playing |
| C．haven't played | D．hadn't played |
In order to find the missing child, villagers __________ all they can over the past five hours.
| A．did | B．do |
| C．had done | D．have been doing |
During the last three decades, the number of people participating in physical fitness programs __________ sharply.
| A．was increasing | B．has increased |
| C．had increased | D．will be increasing |