Phycocyanin.
β-carotene.
Cytochrome-c.
Chlorophyll-b.
Blue-green algae have the blue-green pigment, phycocyanin that serves as antennae in the photolysis of water at photosystem II and acts as a light harvesting complex along with electron carrier. Chlorophyll b is absent in blue-green algae. So, the correct answer is option A.