Which of these best defines “environmental science”?
a the study of how humans interact with the environment
b the study of life
c the study of the properties and changes of matter
d the study of how plants interact with the environment

A or/and D

Explanation:

Environmental science is the study of how organisms interact with their environment so it can be either a or d. I would say a combination of both.

The study of how A. Human interacts with the environment is considered as best definition for environmental science.

Environmental science is the investigation of the cooperation between the physical, concoction, and organic segments of nature. It comprises of various subjects like geography, hydrology, soil sciences, plant physiology, and environment.  

Ecological researchers may have preparing in more than one order; for instance, a geochemist has mastery in both geography and science. With the knowledge of all these filed, the interaction between human and the natural world is researched and studied.  

but there is no

i guess you forgot putting it.