Williams sisters completed their high school_______ developing their tennis careers.
| A．as | B．until |
| C．when | D．while |
He is a student at Oxford University, ____for a degree in computer science.
| A．studied | B．studying | C．to have studied | D．to be studying |
If it ______________ tomorrow, I would stay at home watching TV.
| A．should rain | B．rains | C．was to rain | D．will rain |
Each time ________ they met, they would talk long hours together.
| A．which | B．when | C．during | D．/ |
Though ______ _money, his parents managed to send him to a key university.
| A．lacked | B．lacking of | C．lacking | D．lacked in |
In time of serious accidents, ________ we know some basic things about first aid, we can save lives.
| A．whether | B．until | C．if | D．unless |