以下有关热学内容的叙述,正确的是( )
A:在两分子间距离增大的过程中.分子间的作用力一定减小
B:用NA表示阿伏加德罗常数,M表示铜的摩尔质量,ρ表示实心钥块的密度,那么铜块中一个铜原子所占空间的体积可表示为 MρNA
C:雨天打伞时,雨水投有透过布雨伞是因为液体表面存在张力
D:晶体一定具有规则形状,且有各向异性的特征
E:理想气体等压膨胀过程一定吸热
On Sundays we often go to the1near our school. There are many2 in it—tigers, elephants, pandas and monkeys. The3 are very big. They all have4 noses. Their noses can5 them eat and drink. Tigers are very6. They often run around. They don't like to7 in the zoo. Many people like8. They are animals of China. But I like monkeys most. We like9 to the zoo. We can10 more about animals there.
如图所示,用滑轮组将重为120N的物体匀速提升2m,所用时间为10s,若不计绳子的重力及摩擦,动滑轮重为30N,所用拉力F为____ N,拉力做功的功率为____ W,滑轮组的机械效率为____ .
人的胚胎发育场所是( )