— I phoned you at about three this afternoon, but no one answered.
— Oh, that was probably _______ I was doing exercise outdoors.
| A．when | B．why | C．what | D．that |
【原创】 Vehicles, coal-burning, airborne dust and industrial production ______85 to 90 percent of the major airborne pollution sources in most Chinese cities, the newest research shows.
| A．account for | B．call for |
| C．make up for | D．provide for |
【原创】 Green roofs have an ______effect, helping reduce the amount of energy______ to heat a building in winter and cool it in summer.
| A．isolated；needed | B．isolating；needed |
| C．isolated； needed | D．isolating；needing |
【原创】The hardest thing is to ______ less when you can ______more.
| A．get; take; | B．take; take; |
| C．take; get; | D．get; get; |
We need some more facts and figures we take the final decision.
| A．since | B．after | C．before | D．until |
Only you step into society can you learn practical things.
| A．while | B．that | C．when | D．as |