填料旋塞是利用填料填塞阀体与阀芯之间的间隙而避免漏气，可用于（）管道上。
A、超高压
B、高压
C、中压
D、低压
参考答案：C
I watched the girl step off the sidewalk, ____the road, and ___ into the post office.[ ]
A. crossed; disappear
B. cross; disappear
C. to cross; to disappear
D. crossed; disappeared
高压断路器的用途有哪些？
