How many customer groups should you specify?

Refer to the exhibit.

You are using K-means clustering to classify customer behavior for a large retailer. You need to determine the optimum number of customer groups. You plot the within-sum-of- squares (wss) data as shown in the exhibit.

How many customer groups should you specify?
A . 2
B . 3
C . 4
D . 8

Answer: C