自然灾害逃生时，多人向同一个方向拥挤是很不安全的，因此处在拥挤的人群中时，要向与人流相反的方向移动。
参考答案：错
解析：应与人群同一方向移动。
下列物质中，属于纯净物的是[ ]
A．95%的酒精
B．溶质的质量分数为98%的硫酸
C．含结晶水为36.0%的胆矾
D．含碳酸钙为95%的石灰石
The achievements of the greatest minds in science could never have been reached if it had not been for the patient and accurate work of hundreds of other people.
A．has it not been
B．if it had been
C．if hasn't been
D．had it not been
