求助一题

huahua115

怎么理解？？？

the range of the monthly salary in 1999 is 240, the range of the monthly salary in 2000 is 320, ask what is the minimal range of the monthly salary in both 1999 and 2000. (4次)
A: 80
B: 240
C 320
D: ***
E: ***
参考答案:. 320
思路: 即1999年的range落在2000年间。