Answer: Hemoglobin
Explanation: Hemoglobin is a protein very rich in iron found in red blood cells and is responsible for the transportation of Oxygen from the lungs to the whole body. Oxygen binds to the hemoglobin in red blood cells and the red pigmentation of blood that is highly oxygenated is due to the hemoglobin content found in RBC's.
The walls of xylem cells are lignified (strengthened with a substance called lignin ). This allows the xylem to withstand pressure changes as water moves through the plant.
The cell membrane is flexible because of the presence of oil like substances called phospholipids, which gives it a fluid nature. While as the cell walls are rigid because of the presence of the thick layers of the substances like cellulose in plants, chitin in fungi and peptidoglycon in bacteria.
The black box because black reflects more heat than white
