$(a)$ Draw the structure of a nephron and label the following parts on it:
$(i)$ Renal artery
$(ii)$ Bowman's capsule
$(iii)$ Glomerulus
$(iv)$ Collecting duct
$(b)$ Name four substances in the initial filtrate which are selectively reabsorbed as the filtrate flows along the tubule.

(N/A) The structure of a nephron is shown in the provided diagram,with the renal artery,Bowman's capsule,glomerulus,and collecting duct clearly labeled.
$(b)$ As the initial filtrate flows along the nephron tubule,the following four substances are selectively reabsorbed into the blood:
$(i)$ Glucose
$(ii)$ Amino acids
$(iii)$ Salts (such as $Na^+$,$Cl^-$)
$(iv)$ Water