如图,A,B两点被池塘隔开,在A,B外选一点C,连接AC和BC,并分别找出AC和BC的中点M,N,如果测得MN=20m,那么A,B两点间的距离是多少?( )
A:20m
B:30m
C:40m
D:50m
在探究花生果实大小变异的活动中,某小组的做法不科学的是( )
Since the exchange student was born in America, he simply has no idea life will be like in China.
如图是KNO3和NaCl溶解度曲线,根据如图所指,回答下列问题