A:①
B:②
C:③
D:④
下列哪种生物不能作为生物武器( )
池塘里的睡莲的面积每天长大一倍,若经过12天就可以长满整个池塘,则这些睡莲长满半个池塘需要( )天.
—Very much. He always makes his classes _______.