Which of the following is a physical change?   adding acid to milk to form sour cream  adding enzymes to milk to form cheeseadding bacteria to heated milk to form yogurt  adding sugar to milk to form sweetened milk

Idon’t know how to solve this question

If a solution is considered basic, then a) the hydroxide ion and hydronium ion concentrations are equal. b) the hydroxide ion concentration is less than the hydronium ion concentration. c) the hydronium ion concentration is greater than the hydroxide ion concentration. d) the hydroxide ion concentration is greater than the hydronium ion concentration.

What is the subscript for oxygen in its molecular formula