Which of the following is a common side effect of chemotherapy treatments?

Nausea is indeed a common side effect of chemotherapy treatments. Chemotherapy drugs work by targeting rapidly dividing cells, which includes not only cancer cells but also healthy cells in the lining of the gastrointestinal tract. This disruption can lead to various gastrointestinal symptoms, among which nausea is prominent.

Chemotherapy may also cause vomiting, loss of appetite, and changes in taste, but nausea is one of the most frequently reported side effects experienced by patients. The severity can vary depending on the specific drugs used and the patient's individual response to treatment.

The other options such as hyperactivity, increased hair growth, and improved eyesight are not typically associated with chemotherapy. Instead, chemotherapy often leads to fatigue and hair loss due to its impact on rapidly dividing cells throughout the body, including hair follicles, which explains why those alternatives do not fit the context.