Which of the following led to the greatest decline of bedbug populations in the mid twentieth century?

highly improved laundering soaps.
the use of pesticides, namely ddt.
the increased use of running water in homes.
the use of washing machines.

The answer is the increase use of running water.

Explanation:

The increased amount of water in homes allowed for washing clothes and bedding.

Option B

Explanation:

There was rise in the population of bed bug during the mid twentieth century and there was no control on them.

The use of pesticide was the one and only solution on the pests. DDT was a very effective pesticide that killed bed bugs.

DDT was banned after sometime because it entered the food chain and its level was increasing significantly at each level.

But before that it was very effective in eradicating bed bugs.