Disposable plastic plates should not be used because

What is the layer located at an altitude of $50 \ km$ from the Earth's surface called?

The first trophic level in a food chain is always a green plant. Why?

Which of the following is a top-level carnivore?

Which is the primary factor responsible for the depletion of the ozone layer?

Suggest one word for each of the following statements/definitions:
$(a)$ The physical and biological world where we live in
$(b)$ Each level of food chain where transfer of energy takes place
$(c)$ The physical factors like temperature,rainfall,wind and soil of an ecosystem
$(d)$ Organisms which depend on the producers either directly or indirectly for food