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Choice A is wrong because ciprofloxacin does not inhibit cell wall synthesis.
That is the mechanism of action of beta-lactam antibiotics, such as penicillins and cephalosporins.

Choice B is wrong because ciprofloxacin does not inhibit protein synthesis.
That is the mechanism of action of macrolides, such as erythromycin and azithromycin.

Choice D is wrong because ciprofloxacin does not inhibit folic acid synthesis.
That is the mechanism of action of sulfonamides, such as sulfamethoxazole and trimethoprim.

Choice B is wrong because “enhance the selective toxicity of each drug” means that the drugs would target only the bacteria and not harm the host cells, which is not the main reason for using a combination of drugs.

Choice C is wrong because “increase the penetration of drugs into the lungs” means that the drugs would reach the site of infection more easily, which is not the main reason for using a combination of drugs.

Choice D is wrong because “reduce the adverse effects of each drug” means that the drugs would have less side effects when used together, which is not the main reason for using a combination of drugs. In fact, some of these drugs can have serious side effects such as liver damage, vision loss, or nerve damage.

Choice A is wrong because methicillin does not work by being broken down by an enzyme. Some other antibiotics, such as penicillin, can be inactivated by bacterial enzymes, but not methicillin.

Choice C is wrong because methicillin does not work by entering the bacterial cell. Some other antibiotics, such as tetracycline, can be expelled by bacterial membrane pumps, but not methicillin.

Choice D is wrong because methicillin does not work by blocking an alternative pathway. Some other antibiotics, such as sulfonamides, can be bypassed by bacterial alternative pathways, but not methicillin.

Choice A is wrong because dose-dependent and reversible implies that the adverse effects can be reversed by lowering the dose or stopping the therapy, which is not true for aminoglycosides.

Choice C is wrong because time-dependent and reversible implies that the adverse effects are related to the length of exposure and can be reversed by shortening the therapy, which is also not true for aminoglycosides.

Choice D is wrong because time-dependent and irreversible implies that the adverse effects are related to the length of exposure and cannot be reversed by shortening the therapy, which is partly true but not as accurate as choice B.