—Before he went on the stage,he took a deep ______ .
—He was too nervous.
A:breath
B:smile
C:voice
我国某河流:水量较丰富,每年5月和8月前后有两次汛期,含沙量少,有4﹣5个月的结冰期.该河流位于( )
寒冷的南极地区和北极地区生物种类较少,是因为下列哪种条件不能满足大多数生物的生存所需则( )
图片所代表单词的首字母是____。