请教OG11TH passage1-7

7.One function of the third paragraph of the passage is to

C qualify the extent to which two previously mentioned groups might be similar

我明白这一段比较的是两个group的不同点，上一段说的是相同点，但是我不太明白什么叫qualify the extent？

Qualify the extent to which the previous two points are similar

means

Identify the difference or similarity of the previous two points.

Put it simple, that means he wants you to find the difference.