Which of the following is NOT a reason that coastal areas are densely populated?

These areas are often flat and ideal for farming.
Opportunities for trade.
Coastal plains are often sites of river deltas, which are good areas for farming.
Farming is more difficult in these areas.

Farming is more difficult in these areas.

Is there more than one answer

I apologize for any confusion. The correct answer is:

Farming is more difficult in these areas.