Only after a person has realized the importance of knowledge, ____________.
| A．he can devote himself to learn |
| B．he may devote himself to learning |
| C．can he devote himself to learn |
| D．can he devote himself to learning |
__________the burglar from the second floor when the house owner found him stealing last night．
| A．Down jumping | B．Down jumped |
| C．Jumping down | D．Jumped down |
Playing QQ’s “Happy Farm” by planting, watering, fertilizing, spraying, harvesting and selling of virtual vegetables, fruits and flowers, we can find out _____ all the excitement is about．
| A．that | B．if | C．what | D．when |
A giant helium（氦） balloon is telling residents of Paris how good or bad the air quality is．When it’s good, the balloon ----measuring 22 meters wide and 32 meters high---shines green．_________, it’s red．
| A．Though terrible | B．Whenever good |
| C．If worse | D．When bad |
Sustainable development is long-term ________which focuses on the environment and ________ natural resources．
| A．plan; preserve | B．plan; preserving |
| C．planning; preserving | D．planning ;preserve |
_______ you call me to say you’re not attending my birthday party, I’ll see you at it.
| A．Whether | B．Though | C．Until | D．Unless |