A nurse is caring for a client receiving gentamicin. For which of the following should the nurse monitor the client?

A. Tinnitus: Gentamicin is an aminoglycoside antibiotic that can cause ototoxicity, which includes symptoms such as tinnitus (ringing in the ears). B. Tachycardia: This is not a typical adverse effect of gentamicin. C. Polyuria: Gentamicin does not commonly cause increased urine output. D. Photophobia: This is not a known side effect of gentamicin.