Question

which were popular chemical compounds that were found to be effective insecticides during the 19th century? magnesium and nickel lead and copper pyrethrum and rotenone sulfur and neon

Explanation:

Magnesium, nickel, lead, copper, and neon are either metals or noble gases, not primarily known as 19th - century insecticides. Pyrethrum (a natural insecticide from chrysanthemums) and rotenone (a natural compound from plants) were used as insecticides in the 19th century.

Answer:

C. pyrethrum and rotenone