Ppo
abbr. 聚对苯氧化物（poly - p - phenylene oxide）；胃蛋白酶最大排泄量（peak pepsin output）
🗣️ 情景例句
On a studect visa, full-time work is not permitted.
持学生签证的话，不允许做全职工作。
Don't worry he wiil bring something.
不要担心他会带来什么。
and we have to lower into the ground and haul out of the ground great lengths of drill pipe which are rotated by an engine at the top and are fitted with a cutting bit at the bottom.
我们必须把很长的钻杆一节节地钻入地下，然后再从地下拉出来。钻杆顶部安装的发动机带动钻杆旋转，它的底部装有钻头。