—What the number of the students in your class ?
—About 60 . A number of them girls .
A:is ; is
B:are ;are
C:is ; are
D:are ; is
如图为胡萝卜素粗品鉴定装置和鉴定结果示意图,请据图回答下列问题:
①图中所用的胡萝卜素粗品鉴定的方法名称是____ .
②a的作用是____ .
③A、B、C、D四点中,属于标样的样点是____ .
④乙代表的物质是____.
通常你在电脑上做什么?
____ ____ you usually____ on your computer?