Assertion (A): The leaves of cacti are reduced to spines. Reason (R): Spines reduce water loss by transpiration. MCQ with Answer and Explanation

Explanation:
Cerebrospinal Fluid (CSF) is a clear, watery fluid that circulates through the ventricles of the brain, the central canal of the spinal cord, and the subarachnoid space. It provides mechanical protection (cushioning), chemical stability, and waste removal for the central nervous system. CSF is primarily produced by the choroid plexus, which is a network of highly vascularized, specialized ependymal cells located within the ventricles of the brain (lateral, third, and fourth ventricles).

Explanation:
Oxidative phosphorylation occurs on the inner mitochondrial membrane, where the electron transport chain creates a proton gradient, and ATP synthase uses this gradient to produce ATP. This is the major source of cellular energy. Nucleus stores DNA, Golgi processes proteins, ribosomes synthesize proteins.

Explanation:
Antibodies are produced by B-lymphocytes (plasma cells), not T-cells. They are immunoglobulins that bind specific antigens. Thus, 2 and 3 are correct.