The external flotation bladder of an immersion suit should be inflated（）. ["only after two hours in the water","only after four hours in the water","before entry into the water","upon entry into the water"]
下列现金成本中，属于固定成本性质的是（） ["现金管理成本","持有现金的机会成本","现金交易成本","现金短缺成本"]
简述长棘吻虫病的症状和病理变化。
在涉外巡察中应如何缩小影响避免误会？
简述长棘吻虫病的病原。
开卷落料线由哪几部分构成？各自完成哪些工作？
