Interpreting Dendrogram for hierarchical clustering

Question

Hi I am doing python course from Datacamp. I have difficulty in understanding dendrogram and clustering.

Intermediate clusterings

Question: Displayed on the right is the dendrogram for the hierarchical clustering of the grain samples that you computed earlier. If the hierarchical clustering were stopped at height 6 on the dendrogram, how many clusters would there be?

How do we have 3 clusters if stopping at height of 6

Answer 1

Because there are three partitions remaining if you draw a line at height 6.

This apparently is a class question. It may be better to ask in class: others may have the same problem understanding and your teacher needs feedback what you find difficult!