If All A are B and No B are Z, is the conclusion No A are Z valid?

• A. No, it's invalid.
• B. Yes, the argument is valid.
• C. Only sometimes valid.
• D. It depends on A.

Answer: (B)

The idea being tested is how two categorical relationships combine to produce a new conclusion. If every member of A is contained in B, and B has no members in common with Z, then A cannot have any members in common with Z either. Put simply, A sits entirely inside B, and since B and Z don’t overlap, A can’t overlap with Z. Therefore No A are Z follows in all cases.

So the argument is valid because the first statement guarantees every A is a B, and the second statement guarantees there are no B-Z overlaps, which rules out any A being Z as well. The conclusion doesn’t depend on particular properties of A; it’s a universal consequence of the two given facts.