The chief ingredient of the mosquito repellent cream is derived from

Answer: (b) Neem

Neem oil was the natural base of mosquito-repellent creams (e.g. early herbal creams).

The idea

Neem oil has a strong smell and a bitter taste that insects avoid. Mixed into a cream or burnt in a lamp, it keeps mosquitoes away, so it was the natural base of early repellent creams in India.

Natural repellents: neem oil, citronella and lemongrass oil → Synthetic repellent for skin: DEET → Coils and mats: chemicals modelled on pyrethrum from chrysanthemum flowers

Why the others are wrong

(a) Tulsi repels insects mildly but is not the base of repellent creams.

(d) Rice bran oil is a cooking oil.

The trap

Today lemongrass/citronella is the famous natural repellent (see 2021). In 1989 the answer was neem.

Also know

Neem contains azadirachtin, which can deter insect feeding and disrupt growth; neem products are used as biopesticides. Pyrethrins come from chrysanthemum flowers, while pyrethroids are synthetic chemicals modelled on them. A repellent discourages insects from approaching; an insecticide kills them. Removing stagnant water controls mosquito breeding, while larva-eating fish such as guppies provide biological control.