Question

What is the main idea of this selection?

TA
Overcrowding in the city of Venice has increased its
need for additional sources of fresh water.
Because of flood waters from high tides, the people of
the city of Venice use gondolas and other boats for
transportation.
Water has always played an important role in history for
residents of the city of Venice.
No one is willing to help rescue the city of Venice from
flooding.

Answer 1

overcrowding in the city of venice

Explanation: because most of the time the first sentences tells the paragraph etc.