Refer the given figure of nephron. Identify A, B, C and D and...

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1. AA-Glomerulus - a tuft of capillaries formed by afferent arteriole
2. BB-PCT-reabsorption of $\mathrm{HCO}_3^{-}$and selective secretion of $\mathrm{H}^{+}$and $\mathrm{K}^{+}$occurs here.
3. CC-DCT-almost all glucose, amino acids, water, $\mathrm{Na}^{+}, \mathrm{K}^{+}$and uric acid are absorbed here.
4. DD-collecting duct-extends from the cortex of the kidney to the inner parts of medulla. Large amount of water is secreted in this region.