Only after he realized the significance of mastering two languages __________ English carefully.
| A．did he set about learning | B．did he set out learning |
| C．had he set about learning | D．had he set out learning |
During enjoying the Mid-Autumn Festival, celebrating the harvest is an important reason, but of __________ importance is the whole family’s get-together.
| A．fair | B．reasonable | C．equal | D．proper |
Trains with the first letter D or Z can run __________ a speed of more than 200 kilometers an hour when it travels __________ the desert.
| A．with; cross | B．in; through | C．at; across | D．for; in |
People try to avoid public transportation delays by using their own cars, and this _________ creates further problems.
| A．in turn | B．in case | C．in result | D．in short |
_______, they will meet you at the airport but if they can’t arrive on time, you can take a taxi instead.
| A．If any | B．If so | C．If possible | D．If ever |
As time went by, the plan stuck ______ fairly practical.
| A．to proved | B．to proving | C．proved | D．to be proved |