2 . The new tax law came into effect last May, _____ white-collar workers have benefited a lot from it.

A．when

B．through which

C．for that

D．since when

3 . On the eve of the Spring Festival, I usually stay up until midnight, ________I can set off the firecrackers and fireworks.

A．which

B．when

C．where

D．who

4 . The final proof came when an enormous shipyard was discovered in Nanjing, ______ the fleet had been built. （根据句意填空）

5 . 春暖花开的四月是欣赏这个南方小镇美景的最佳时机。（when) （汉译英）

6 . Daylight saving time begins at 2: 00 a. m. local time on the second Sunday in March, ________clocks spring forward an hour, typically ________observers to lose an hour of sleep.

A．which, caused

B．when, causing

C．which, causing

D．when, caused