Brown stains in vessels and clothes indicate the presence of high quantities of ________ in water. A. Magnesium B. Calcium C. Manganese D. None of these

The correct answer is: C. Manganese

Manganese is a naturally occurring mineral that can be found in water. It is a essential nutrient for humans, but high levels of manganese can cause health problems. Manganese can also cause brown stains on vessels and clothes.

Magnesium and calcium are also minerals that can be found in water. However, they are not as likely to cause brown stains as manganese.

Option D is incorrect because manganese is a mineral that can be found in water.