【单选题】使用止血带进行包扎止血时,下列做法错误的是
A.
每小时最好放松一次止血带,松解时间3~5分钟即
【单选题】下列关于使用止血带时的注意事项,说法错误的是
【简答题】A typist types four envelopes and four letters. She places the letters in the envelopes at random. What are the chances that only three letters are in their correct envelopes?
【简答题】函数 f ( x )=sin(2 x - )-2 sin 2 x 的最小正周期是 .