PS II contains a non-chlorophyllous pigment in blue-green algae
A) Beta-carotene
B) Zeaxanthin
C) Phycocyanin
D) Cytochrome

Hint: It is basically the protein pigment complex and mostly found in the cyanobacteria. It has a single absorption peak. They can also be used as tracers in genetics because of its natural fluorescence.

Complete Answer:
- PS II which is known as photosystem II is the very first complex of protein present in the light-dependent reactions of photosynthesis. They are located in the thylakoid membrane of algae, cyanobacteria, and plants.
- Photosystem II provides electrons for the process of photosystem. There are two types of the photosystem i.e. photosystem I and photosystem II. In the photosynthetic bacteria which are anaerobic in nature only photosystem I can be found whereas blue-green algae or cyanobacteria contains both type of photosystem i.e. I and II.
- Only one chlorophyll present in the photosystem I. On the other hand, photosystem II contains various phycocyanin and yellowish carotenoids that have different colours which are present in different species. Phycocyanin is mostly found in the cyanobacteria that have a single absorption peak.

Thus, the correct answer is option C i.e., Phycocyanin.

Additional information:
- Beta-carotene contains the red-orange pigment that is found in various plants and animals. Examples are: carrots and other vegetables.
- Zeaxanthin are the carotenoids in nature containing saffron, corn and paprika colour.
- Cytochromes are the proteins that are redox-active containing a heme. There are 4 types of cytochromes i.e. a, b, c, d.

Note: Phycocyanin found in the cyanobacteria belongs to the phycobiliproteins. It is a biologically active compound that is purified from the variety of seaweeds. It acts as an antenna in blue-green algae photosynthesis.