Which one of the following is used in preparing a natural mosquito repellent?

Shows that certain grasses (e.g., lemon and ginger-grasses) yield medicinal and perfumed oils used for practical purposes.

A student could note that some grasses produce volatile oils with bioactivity and therefore test whether Parthenium also yields similar oils usable as repellents.

Lists plants/spices whose parts are used as medicines or insecticides (e.g., pepper oil used in insecticides), illustrating that plant extracts are a documented source of insect-repellent/insecticidal compounds.

One could reasonably check whether Parthenium contains compounds analogous to those in listed species or has been used similarly in folk practice.

Gives an explicit example of preparing natural pest repellents from plants (neem and garlic) in a real farming context.

This supports the idea that communities adopt locally available plants for repellents, so a student could survey local uses of Parthenium as a next step.

Mentions pest management strategies through natural repellents and plants grown together as part of sustainable agriculture.

Suggests a framework: where natural repellents are part of practice, investigate whether invasive/weedy species like Parthenium are among locally used repellent plants.

Describes prevention of mosquito-borne disease including use of repellents as a recognized control measure.

Combining this general need for repellents with evidence that plants can provide repellents motivates targeted tests (laboratory or ethnobotanical) of Parthenium for repellent activity.