Fresh milk has a $pH$ of $6$, when milk changes into curd, the $pH$ will:

The correct option is B Become less than $6$
When milk changes into curd, the $pH$ value will change. Since the $pH$ value of milk is $6$ it is acidic in nature. When milk converts into curd due to action of bacteria, lactic acid is formed which is more acidic in nature. Therefore, the $pH$ value of milk reduces as it turns into curd.