当燃油压力高于进气歧管内的压力300Kpa时，燃油压力调节器内的弹簧被油压顶起，燃油得以释放回流。
参考答案：对
The boy __________ his dog well every day. [ ]
A. looks for
B. looks after
C. looks like
D. look after
中心静脉穿刺的指征有哪些？
