Pamela watches her cat Mr. Big swat his paw at the wall and calls out, "Crazy Big, what are you swatting at; nothing is there." How would you explain the fact that Mr. Big can see something that Pamela cannot?

a. Cats see low-frequency, low contrast objects better than humans.

b. Cats see low-frequency, high contrast objects better than humans.

c. Cats see high-frequency, low contrast objects better than humans.

d.ats see high-frequency, high contrast objects better than humans.