Question

in order for a physical barrier to be effective in preventing infection, the barrier must ____________. a. prevent the substance from entering the body, trap the substance when it first enters the body, or flush the substance out of the body b. destroy the substance before it enters the body, prevent the substance from reproducing, or flush the substance out of the body c. trap the substance in the body, remove the substance from the body, or prevent the substance from reproducing d. flush the substance from the body, transport the substance in the body, or destroy the substance in the body please select the best answer from the choices provided. a b c

Explanation:

Physical barriers in the body's immune system, like skin, mucous membranes, etc., work by preventing pathogens (the "substance" here) from entering (e.g., skin as a barrier), trapping them when they first try to enter (e.g., mucus in respiratory tract traps particles), or flushing them out (e.g., tears wash away foreign substances from the eyes). Options B, C, and D have incorrect actions such as "destroy the substance before it enters" (physical barriers don't destroy, they just prevent entry/trap/flush), "prevent from reproducing" (that's more of an immune - cell function like macrophages or antibodies in some cases, not physical barrier's main role), and "transport the substance in the body" (opposite of what a barrier should do).

Answer:

A. prevent the substance from entering the body, trap the substance when it first enters the body, or flush the substance out of the body