What is the main idea of this passage?

Question

Responses
A In order to help preserve and protect our environment, builders should construct more "green" buildings.In order to help preserve and protect our environment, builders should construct more "green" buildings.
B One way a building can be more green is by the use of passive solar heating to decrease the use of electricity.One way a building can be more green is by the use of passive solar heating to decrease the use of electricity.
C Reducing the amount of fresh water used in building is another way that builders can help protect the environment.Reducing the amount of fresh water used in building is another way that builders can help protect the environment.
D One way a building could be more green is through the use of green roofs and walls to reduce heating and cooling costs.

Answer 1

The main idea of this passage is that there are various ways builders can construct more "green" buildings to help preserve and protect the environment.