_________ are circular and biconcave for easy passage through blood capillaries and to transport oxygen.

Correct option is B

The correct answer is (b) Red blood cells

• Red blood cells (RBCs) are biconcave in shape, which helps them pass through narrow blood capillaries more efficiently.

• Their biconcave shape increases the surface area for oxygen transport and allows them to squeeze through small capillaries without breaking.

• The main function of RBCs is to carry oxygen from the lungs to tissues and organs and bring carbon dioxide back to the lungs for exhalation.

• Their flexible structure and lack of nuclei help in maximizing oxygen-carrying capacity.

Information Booster:
• RBCs are made up of hemoglobin, a protein that binds to oxygen and carbon dioxide.
• The biconcave shape of RBCs is vital for their function and efficiency in oxygen transport.
• Guard cells (A) are specialized plant cells involved in regulating stomatal opening for gas exchange.
• White blood cells (WBCs) (C) are part of the immune system and do not have the same shape or function as RBCs.
• Nerve cells (D), also called neurons, transmit electrical signals but are not involved in oxygen transport.

Additional Information:

• (A)Guard cells are involved in water regulation and gas exchange in plants, not oxygen transport in animals.

• (C)White blood cells are involved in immune responses and do not carry oxygen.

• (D)Nerve cells are responsible for transmitting electrical impulses but do not have the function of oxygen transport.