However, the systems are independent （独立）and there is no fluid exchange between them.然而, 这些系统是独立的，它们之间没有流体交换。
A.However, the systems are independent of each other, and they do not exchange fluid. B.However, the systems depend on each other and they cant exchange fluid. C.The systems exchange fluid from each other and so they are independent.正确答案A
