Question

the smallest particles that make up matter
a. are about the size of marbles.
b. are about the size of pinheads.
c. can be seen with the unaided eye only at certain temperatures.
d. are too small to be seen with the unaided eye.

Explanation:

The smallest particles that make up matter are atoms and sub - atomic particles like protons, neutrons, and electrons. These are extremely tiny. Marbles and pinheads are macroscopic objects. Atoms and sub - atomic particles cannot be seen with the unaided eye under any normal circumstances as they are on the scale of picometers or smaller.

Answer:

D. are too small to be seen with the unaided eye.