Wormseed is a small, perennial tropical herb with a grooved, branched, reddish stem and a strong, disagreeable scent, growing up to four feet tall. It is native to Central, South America, and the Caribbean, but is now extensively cultivated in China and in the United States. The summer blooms produce small black seeds, and by autumn these seeds contain a toxic essential oil. The most common use of wormseed is for parasitic infections. The active ingredient in wormseed is ascaridole, which is a volatile oil. Chenopodium oil is consumed as an oral antiparasitic against roundworms and hookworms
So, the correct answer is 'Chenopodium oil'.