the tip of the iceberg

This is our third idiom containing a “winter” word. Do you know “the tip of the iceberg”?

Look at the conversation below. Can you guess the meaning?

Robert: It seems like your company has some problems. I heard a lot of people are quitting your company.

Sean: That’s just the tip of the iceberg. We have lost all of our main customers over the past year, and have a lot of debt!

Does it mean:

a) the biggest problem

b) a small part of the problem

c) the most urgent problem

The answer is below! ↓

Answer: b) a small part of the problem