Question

which of these is a source for particulate matter in the air?
a. automobiles
b. dust
c. fires
d. all of the above
please select the best answer from the choices provided.
a
b
c
d

Explanation:

Automobiles emit particulate matter from exhaust. Dust is particulate matter itself. Fires produce soot and ash which are particulate matter. So all are sources.

Answer:

D. all of the above