1. This boost in reaction time after exercise training may occur because declines associated with getting old could actually stem from declines in physical condition.
    接受运动训练之后，人的反应速度会加快，这可能是因为与衰老有关的机能衰退实际上根源于体质下降。

2. He soon detected the faulty valve.
    他很快查出了出毛病的阀门。

3. I couldn´t stem the bleeding.
    我无法止住流血。