【简答题】Diaphragm valves use a flexible and to regulate flow. The handwheel operates just like the handwheel on valve. The is attached to a device called the . The compressor pushes on a flexible diaphragm. T...
【单选题】听力原文:M: I'd dike some red roses. W: Is it your wife's birthday? M: No, it's our wedding anniversary. She really likes roses. So I give her some every week. I just wish they would stay fresh longer tha...