13.
A:
any solid, liquid or gaseous substance present in such concentration as may be, or tend to be, injurious to environment
B:
any substance present in such concentration as may be, or tend to be, injurious to environment
C:
any solid, liquid or gaseous substance present in such concentration as may be, or tend to be, injurious to a person
D:
any solid, liquid or gaseous substance present in such concentration as may be, or tend to be, injurious to the society
The answer is: A