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.

Snippet states that certain grasses (lemon and ginger-grasses) yield medicinal and perfumed oils, showing grasses can be sources of useful volatile compounds.

A student could check whether elephant (Napier) grass likewise produces essential oils or extracts and then look for any studies or folk uses testing those extracts for mosquito-repellent activity.

Snippet notes pest management strategies that include natural repellents and specific plants grown together, implying plant-based repellents are a recognized, practical approach.

Use this general rule to search agricultural or ethnobotanical sources for records of elephant grass being used as a companion plant or processed into repellents.

Snippet lists 'Napier grass' among common grasses; Napier grass is commonly known (by basic outside knowledge) to be the same as elephant grass, linking the common name to a listed grass type.

A student can use the Napier–elephant grass identity as a keyword pair when searching literature or local-use reports for repellent preparations.

Snippet describes elephant grass as a tall, coarse grass typical of savanna environments, indicating it is abundant in some regions and thus a plausible candidate for local use or experimentation.

Combine this with knowledge of local folk practices (regions where the grass grows) to investigate ethnobotanical uses, including any use as a mosquito repellent.

Lists Cyperus rotundus among weeds with medicinal properties, indicating the plant is used traditionally for therapeutic purposes.

A student could investigate whether medicinal/therapeutic uses of Cyperus rotundus include volatile oils or extracts that might have insect‑repellent properties.

Names aromatic plants (lemon grass, citronella, palmarosa, mint) which are known sources of plant-based repellents or perfumed oils.

A student could use the known example of citronella (an aromatic grass used as a repellent) to ask if other aromatic/medicinal grasses (like Cyperus species) are similarly used.

Notes that certain grasses (lemon, ginger-grasses) yield medicinal and perfumed oils, establishing a pattern that grasses can be sources of bioactive/volatile oils.

A student could test whether nut grass produces an extract/oil comparable to these grasses and whether that oil repels mosquitoes.

Gives a concrete example (neem and garlic) of plants being used to prepare natural pest repellents in practice.

A student could treat Cyperus rotundus analogously—check ethnobotanical records or simple household recipes for its use as a repellent.

States that pest management strategies include natural repellents and planting certain plants together, framing a general practice of using plants for pest control.

A student could search for whether nut grass is recommended in such sustainable pest‑management lists or companion planting guides for mosquito control.