A:启普发生器是块状固体与液体试剂在常温条件下起反应制取气体的典型装置
B:实验开始时先从装置中a处加液体药品,再从b处加固体药品,实验结束后从c处倒废液
C:使用前,应先检查装置的气密性
D:启普发生器有随开随用,随关随停的优点
下列关于弹力的说法中,正确的是( )
— People can find _____ useful information on the Internet.
— Yes. It's important ____ to use computers.
A
Ann is a basketball star. She is 18 years old. She usually gets up at six o'clock. She eats breakfast at seven. Ann and her friends usually play basketball from eight to twelve o'clock. At twelve o'clock she has lunch. School starts at two o'clock, she plays basketball again. At six thirty she has dinner. Ann usually does her homework at eight. At nine thirty she watches TV. Ann usually goes to bed at eleven. Basketball is her life!
根据短文内容,判断句子正误。
当一小块金属钠久置在潮湿的空气中,可能有如下现象产生:①生成白色粉未;②表面变暗;③生成白色块状固体;④发生潮解,表面产生液体。这些现象的先后顺序为( )