Which of the following is a risk factor for head and neck cancer?

The correct answer identifies tobacco use as a significant risk factor for head and neck cancer. Tobacco contains a variety of harmful chemicals that can damage the cells in the mouth, throat, and surrounding areas. This damage increases the likelihood of mutations that can lead to cancerous growth. It is one of the most well-documented environmental risk factors and is particularly associated with cancers of the oropharynx, larynx, and other parts of the head and neck.

The other options do not contribute to an increased risk for head and neck cancer. Regular exercise is generally associated with numerous health benefits, including a reduced risk of various cancers. Increased fluid intake is vital for overall health and can help in maintaining oral and throat moisture, which is beneficial rather than detrimental. Lastly, a low-fat diet can be part of a healthy lifestyle, minimizing the risk of chronic diseases but not specifically linked to an increased risk of head and neck cancers.

In summary, the correlation of tobacco use with increased cancer risk makes it a key factor to consider in understanding head and neck cancer development.