Enzymes and Proteins

[Raltman1A]

In question 9 in the 2015 workbook quiz the question states "which of the following statements about enzymes is incorrect?"
I understand that choice D is the most incorrect answer because obviously every protein is not an enzyme, however, isn't choice C technically incorrect as well? Ribozymes are enzymes that use catalytic RNA to catalyze reactions, so not all enzymes are proteins. I understand this is not an LS course, but I want to clear up any confusion.

[Chem_Mod]

But then the question would have used the term "ribozymes".
"Enzymes" still holds true.