A. lactic acid
B. citric acid
C. acetic acid
D. carbonic acid
Submitted by: Abid Hussain
Lactic Acid
Like many other things, milk contains bacteria, Milk also naturally contains a kind of sugar known as lactose.
The bacteria that live in milk get energy from this special sugar and use it to reproduce to make even more bacteria.
When the bacteria use the lactose sugars to reproduce, they change it from lactose sugar into lactic acid, which tastes sour.