When a person is suffering from a severe cold, he or she cannot (a) differentiate the taste of an apple from that of an ice cream (b) differentiate the smell of a perfume from that of an agarbatti (c) differentiate red light from green light (d) differentiate a hot object from a cold object

(b) differentiate the smell of a perfume from that of an agarbatti

Olfactory receptors get blocked in the cold, making it difficult to distinguish smell.