Concept:Glomerular filtration depends mainly on molecular size, allowing small substances to pass into the Bowman's capsule.
Explanation:Blood entering the glomerulus is under high pressure, so plasma components are filtered into the Bowman's capsule.
Small molecules such as vitamins, water, glucose, and mineral salts pass easily through the filtration membrane.
Large molecules like plasma proteins and blood cells are too big to be filtered, so they remain in the blood.
Vitamins are low molecular weight substances, so they are present in the glomerular filtrate.
Their presence in the filtrate does not depend on being fat soluble or on the amount required by the blood.
Most vitamins can later be reabsorbed in the renal tubules.
Answer:A. they have low molecular weight.