An obstruction in the afferent arteriole would reduce the flow of blood into the

Glomerulus

Explanation:

An afferent arteriole is the portion of the renal vein or blood vessel which brings the blood to the glomerulus. The glomerulus is a structure formed inside the Bowman capsule by the capillaries.

The afferent arteriole is involved in bringing the deoxygenated blood to the glomerulus for filtration and also in maintaining the blood pressure of the body. The afferent arteriole is innervated by the sympathetic nervous system, therefore, they can vasodilate and construct in conditions.

Thus, glomerulus is the correct answer.