Question

Why does the teacher keep telling us not to let water collect anywhere in the neighbourhood?

Answer 1

Because it makes a suitable atmosphere for the growth of germs and bacteria which will cause diseases

Answer 2

Answer: Teacher keeps telling us not to let water collect anywhere in the neighbourhood in order to prevent the spread of various diseases.

Standing water or the water collected in containers that are open is the source of breeding of various mosquitoes that can transmit dangerous diseases like dengue and malaria.    

For example- Female Aedes aegypti mosquito ( infected by the dengue virus) transmit the dengue virus by biting an uninfected person.