How do residual pesticides differ from knockdown products?

• A. Both have identical actions.
• B. Knockdown products leave long-lasting residues.
• C. Residual pesticides remain active after application; knockdown products kill pests quickly on contact or shortly after exposure.
• D. Residual pesticides kill pests instantly but fade quickly.

Answer: (C)

The idea being tested is how the action of a pesticide differs in speed and how long it lasts after application. Residual pesticides stay active after you apply them, continuing to affect pests that come into contact with treated surfaces or residues for days, weeks, or even longer. Knockdown products, on the other hand, cause a rapid kill—pests are killed quickly on contact or soon after exposure—but they don’t generally provide long-lasting residual protection. That combination makes the statement describing residuals as remaining active after application and knockdowns as fast-acting on contact the best description. The other options describe either identical actions, incorrect persistence, or opposite timing, which doesn’t match how these products actually work.