A:It's time for breakfast.
B:It's time for lunch.
C:All right.
As is known to us all, taking exercise is b____ to our health.
把墨汁用水稀释后取出一滴放在高倍显微镜下观察,每隔30秒把炭粒的位置记录下来,然后用直线把这些位置按时间顺序连接起来,得到如图所示的图象.下列说法正确的是( )
关于光谱分析,下列说法中不正确的是()