Which statement about surface film agents is NOT true?

Which statement about surface film agents is NOT true?

• A. They form a film on the water that suffocates larvae
• B. They block the siphon's respiration
• C. They are effective only against adult mosquitoes
• D. They are effective in the larval and pupal stages

Answer: (C)

Surface film agents work by spreading a thin film over the water surface, which interferes with how mosquito larvae and pupae breathe. These immature mosquitoes come to the surface to gulp air or to use their siphons, so the film disrupts their respiration and can suffocate them. Because the target of this method is the aquatic stages, these agents are effective in the larval and pupal stages, not against adults. Therefore, the statement claiming they are only effective against adult mosquitoes is not true. The other points—forming a film on the water and suffocating larvae, and blocking siphon respiration—are consistent with how these products work.

Surface film agents work by spreading a thin film over the water surface, which interferes with how mosquito larvae and pupae breathe. These immature mosquitoes come to the surface to gulp air or to use their siphons, so the film disrupts their respiration and can suffocate them. Because the target of this method is the aquatic stages, these agents are effective in the larval and pupal stages, not against adults. Therefore, the statement claiming they are only effective against adult mosquitoes is not true. The other points—forming a film on the water and suffocating larvae, and blocking siphon respiration—are consistent with how these products work.