Confusion question in mock text - help needed!

Hello,

I was doing mock test from mlapshin, and there was this question:

Imagine you are a Scrum Master. There are 10 professional (developers and QA) and the Product Owner. How to distribute people between development teams? Choose all applicable variants:

1) 1 team of 10 people (because there is no reason to divide)

2) 2 teams of 6 and 4 people (the professionals after a short meeting decided this is the best variant)

3) 2 teams of 6 and 4 people (because it is good to have all the QAs in a separate team)

4) 3 teams of 4,3 and 3 people (each team is cross-functional)


And the correct answers are 2 and 4.

However, I disagree with 4th answer. After reading the Nexus guide, it became really clear that with more teams there is more complexity: "If they work in different teams, how will they integrate
their work and test the Integrated Increment? These challenges appear when two teams are
integrating, and become significantly more difficult with three or more teams."

So, why is the answer 4 correct if 3 teams creates more complexity? I'd just choose (2) - I don't see any other correct answers here.

Anyone has a different insight?