Suppose that instead of light waves, we fired electrons through Young's double-slit apparatus. If we fire them one at a time, each electron must either go through one of the slits, or be blocked. The electrons that go through a slit will leave a lasting visible dot on the observing screen (like an x-ray). After doing this for a long while, what might we expect to see on the observing screen?

a) Oddly enough, it would depend on whether we are monitoring which slit each electron goes through or not.

b) We would see two large blobs directly behind each slit.

c) We would see a diffraction pattern as if it were a light wave.

d) We'd see a single bright blob in the center.