民用建筑通常组成部件有（）A、抹灰 B、门窗 C、地坪 D、屋顶 E、楼梯 F、楼板层G、墙体

Skin-diving(潜水) is a new sport today. This sport takes you into a wonderful new world. It is like a visit to the moon. When you are under water, it is easy for you to climb big rocks, because you are no longer heavy.

Here, under water, everything is blue and green. During the day, there is lots of light. When fish swim nearby, you can catch them with your hands.

When you have tank (罐) of air on your back, you can stay in deep of water for a long time. But you must be careful when you dive into deep water.

To catch fish is one of the most interesting parts of this sport. Besides, there are more uses for skin-diving. You can clean ships without taking them out of the water. You can get many things from the deep sea.

Now you see that skin-diving is both useful and interesting.

小题1:Skin-diving is a new sport that_____________.

A．will take you to the moon

B．will take you to a new world of land

C．will take you to the mountain

D．will take you to the deep water小题2:You can climb big rocks under water easily because _________.

A．you are very heavy

B．you are as heavy as on the land

C．you are not as heavy as on the land

D．you have no weight at all小题3:With a tank of air on your back, you can _________.

A．catch fish very easily

B．stay under water for a long time

C．climb big rocks

D．have more fun小题4:Which of the following statement is not true?

A．Skin-diving is a new sport

B．skin-diving is like visiting the moon

C．The only use of skin-diving is to have more fun

D．Skin-diving is not only interesting but also useful.小题5:Skin-diving is a useful and interesting sport because ________.

A．you can catch fish with your hands.

B．you can clean the ship in the water

C．you can get many things from the deep sea.

D．all of the above

人体的八大系统主要在         和         的调节下共同完成各项生命活动。

能最体现材料是否经久耐用的性能指标是( )。

A．抗渗性

B．抗冻性

C．抗蚀性

D．耐水性

发电机、励磁机磁场中心不对称可引起机组振动，有些还会引起发电机定子的振动

基因型为AaBb的水稻（24条染色体）的花药通过无菌操作，接入试管后，在一定条件下培养形成试管苗。

愈伤组织分化是指愈伤组织形成芽和根，再由芽发育成叶和茎。这一过程必须给予光照，其原因是①（）；②（）。