A:南美洲和南极洲的分界线是麦哲伦海峡
B:南美洲和北美洲的分界线是巴拿马运河
C:亚洲和非洲的分界线是波斯湾、苏伊士运河
D:非洲和欧洲的分界线是直布罗陀海峡、地中海、土耳其海峡
A survey was made about what to do if there was a fire. These are some of the replies.
fx=3a-1x+4a,x<1-ax,x≥1在-∞,+∞上是减函数,则a的取值范围是( )
我国陆地面积在世界各国中,仅次于( )