yes

note that the empty set is a subset of any set, except perhaps the empty set ...now there's some food for thought2.) Suppose D is a proper subset of E;

Determine the least possible # of elements that are in D.

I'm assuming this is 1?

i wrote nonsense here, see my next post3.) If D is a subset of E, are we able to say D is a proper subset of E?

I'd say NO but my example I tried given contradicted itself.

EDIT: see red