In a prokaryotic cell, most ribosomes are
a) in the nucleus.
b) attached to the er.
c) attached to the nucleus.
d) floating freely in the cytoplasm.

Correct D). Floating freely in the cytoplasm.

A prokaryote is an organism which does not have the nucleus and almost no membranous organelles. The nucleus is found only in eukaryotes, and each and every cell require ribosomes in order to make proteins.

Since there are no membrane-bound organelles found in prokaryotes, the ribosomes float freely in the cytoplasm.

Hence, the correct answer would be option D.

allowed for the prediction of the properties of missing elements.