pH of milk of magnesia is __________.

Correct option is C

Magnesium hydroxide is a weak base and has a pH of 10.
 Milk of magnesia is a suspension of magnesium hydroxide in water.
 However, the pH of the milk of magnesia is slightly higher than the pH of magnesium hydroxide due to the presence of other alkaline compounds in the suspension.
 It is used as an antiacid.