The Surprising Feature of the Double- Slit Experiment with Electrons

The surprising feature of the double- slit experiment with electrons is

A) when one slit is open, the impact pattern on the viewing screen is an interference pattern, but this interference pattern vanishes when both slits are open.
B) when both slits are open, the impact pattern on the viewing screen is an interference pattern.
C) when both slits are open, the electrons make precise, tiny impacts on the viewing screen.
D) when both slits are open, each individual electron impact on the viewing screen is spread out over a wide area.
E) the overall pattern formed by many impacts is different each time that the experiment is performed, and is thus entirely unpredictable.