The correct option is A proximal convoluted tubule
Urine formation involves three processes - ultrafiltration, reabsorption and secretion.
Reabsorption is necessary to prevent loss of essential nutrients in urine. Around 99 percent of filtrate formed is reabsorbed. Reabsorption can take place in different segments of nephron. Nearly all of the essential nutrients, and 70-80 percent of electrolytes and water are reabsorbed by proximal convoluted tubule (PCT). PCT is the highly coiled structure found next to Bowman’s capsule.
Bowman’s capsule is a cup-like structure that encloses glomerulus. Bowman’s capsule is involved in ultrafiltration.
Distal convoluted tubule (DCT) is another highly coiled tubule which finally opens into collecting duct. DCT is involved in reabsorption of HCO−3.