The red pigment in erythrocytes is which transports oxygen.
hemoglobin
phycoerythrin
carotenoid
chlorophyll

Hemoglobin

Explanation:

The blood is a living tissue made up of cells. These cells include red blood cells or erythrocytes, white blood cells or leukocytes, platelets etc. However, the red blood cells or erythrocytes contains a protein that confers its red coloration upon it. This protein is called HEMOGLOBIN.

Hemoglobin is a protein that contains iron (Fe) element in the core of its structure. Hemoglobin is capable of forming a bond with oxygen molecule, hence, it helps the red blood cells to carry oxygen across the body.

volcanoes (an event in the geosphere) release a large amount of particulate matter into the atmosphere. these particles serve as nuclei for the formation of water droplets (hydrosphere). rainfall (hydrosphere) often increases following an eruption, stimulating plant growth (biosphere).