Cyanobacteria are
are eukaryotes and the earliest type of algae

Oa.
are chemoautotrophs
b.
photosynthetic bacteria
O
are the only prokaryotes that can use photosynthesis
O
not an important part of the carbon cycle
O

Photosynthetic bacteria.

Explanation:

Cyanobacteria also called Photophyta are photosynthetic bacteria even some are nitrogen-fixing bacteria. Cyanobacteria have internal membranes. These are flattened sacs called thylakoids where photosynthesis is performed.

igneous rocks which formed by the crystallization of magma at the surface of the earth called extrusive rocks. they are characterized by fine-grained textures because the rapid cooling at or near the surface did not provide enough time for large crystals to grow.