水与我们息息相关,下列关于水的认识正确的是( )
A.冰的密度大于水的密度
B.淡水资源取之不尽
C.使用无磷洗衣粉有利于防止水体富营养化
D.硬水与肥皂作用易起泡沫
答案:C
卸载回路属于()回路。
A.方向控制回路
B.压力控制回路
C.速度控制回路
用所给单词的适当形式填空。
1. In 1809, Santa had eight ________ (reindeer).
2. Most animals run on four ________ (foot).
3. —What's your _______? —1.88m. (high)
4. Her grandfather told her not ________ (water) the flowers if it rained.
5. Our class could play soccer for a week without ________ (stop).