Prokaryotes used to be classified into one group, but now they are classified in the domains bacteria and archaea.
a. true
b. false

True.

Explanation:

Three domains of life are prokarya, eukarya and archae. Prokaryotes are the organism that lacks the well developed nucleus and membrane bound cell organelle.

Earlier the prokaryotes are classified in the one group. But the prokaryotes are now further classified into the domains archaea and bacteria. As prkaryotic organism shows the similar characteristics with the archae and prokarya. To make the study more simpler, prokaryotes are splits into the domains of bacteria and archaea.

Thus, the answer is true.