A:a
B:/
C:the
D:an
函数f(x)=3tan(x2-π4),x∈R的最小正周期为( )
指出下列说法不正确的一项( )
读岩石圈物质循环示意图,回答下列各题。
If you are planning to spend your money having fun this week, better ________ it—you've got some big bills coming.