It was not until 1911, _______ the first vitamin was identified, _______ people realized the importance of it．
| A．when; which | B．when; that |
| C．that; which | D．that; that |
34．Take the lift to the eighth floor and turn right. You_______have any trouble finding my office.
| A．needn’t | B．mustn’t | C．don’t | D．shouldn’t |
33．The highway through the rain forest was completed in 1990, _________some animal species have died off.
| A．by when | B．since then | C．since when | D．by which time |
32．With so many trees and flowers_____about, our school campus looks like a beautiful garden.
| A．planted | B．to be planted | C．planting | D．being planted |
31．_________reasonable, the idea he to create a friendly environment attracted much public attention.
| A．Sounded; came about | B．Sounded; came across |
| C．Sounding; came up with | D．Sounding; came along |
30．We think that it’s love, generosity and perseverance______make the worldit is today.
| A．what; that | B．that; what | C．which; what | D．which; that |