Archaea and bacteria are similar in which of the following ways?
a. they are prokaryotes.
b. they reproduce by binary fission.
c. they are believed to be the ancestors of plants.
d. they have a cell membrane made of unusual lipids.

Option A and B.

Archaea and bacteria are prokaryote and reproduce by binary fission.

Explanation:

Archaea are grouped of single celled organisms that have no cell nuclei. They are prokaryotes and reproduce by binary fission. They were formally grouped as bacteria with the name archaeabacteria but the classification is outmolded. They are now renamed as archaea bacteria as they are closely related to eukaryotes.

Bacteria also are single celled, microscopic organisms. They are prokaryotes and they reproduce by binary fission. They have are number of shapes ranging from spheres to rods.