Concept: All carbon atoms in the given molecule form only single bonds, so each is sp3 hybridised. Explanation: The structure is: HO−CH2−CH2−CH(CH3)2 It contains: • Two CH2 carbon atoms • One CH carbon atom • Two CH3 carbon atoms Total sp3 hybrid carbon atoms: 2+1+2=5 Thus, the correct option is D. Answer: 5