What makes plants the beginning of the food chain? a) only plants use solar energy in a chemical process to produce food. b) plants make food for other organisms. c) plants can store chemical energy as glucose. d) all organisms eat plants. i think it might be c.

A) Only plants use solar energy in a chemical process to produce food.  

Explanation:

The primary source of energy on Earth is Sun. Green plants are at the beginning of food chain because only green plants can convert solar energy to a form which can be consumed by animals. Plants make food in process known as photosynthesis where in sunlight is used to convert carbon-dioxide and water to form glucose and oxygen. This glucose is eaten by animals from which they get energy to do work. Smaller animals are eaten by bigger continuing the food chain ahead.

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.