The correct answer is option 2, Parkinson`s disease. Parkinson`s disease is a neurodegenerative disorder that affects movement control. While it is not directly caused by the presence of excess arsenic in water, long-term exposure to high levels of arsenic can increase the risk of developing Parkinson`s disease.

Option 1, Alzheimer`s disease, is a progressive brain disorder characterized by memory loss and cognitive decline. There is no direct link between excess arsenic in water and the development of Alzheimer`s disease.

Option 3, skin cancer, can be caused by excessive exposure to ultraviolet radiation from the sun or artificial sources like tanning beds. Arsenic exposure can increase the risk of developing certain types of skin cancer, but it is not the only cause.

Option 4, indigestion, refers to discomfort or pain in the upper abdomen caused by problems with digestion. Excess arsenic in water can potentially lead to gastrointestinal issues, but it is not solely responsible for indigestion.

Overall, while excess arsenic in water may increase the risk of developing certain health conditions, it is important to note that these conditions are multifactorial, and arsenic exposure alone is generally not the sole cause.