Right choice is (a) How to take the medicines
Easy explanation: A prescription has 3 parts. The 1^st part contains the name of the medicine, formulation which is to be taken, strength of the medicine that is to be taken. For example, if the prescription is for amoxicillin the 1^st part will be Rx Amoxicillin caps 500 mg. The 2^nd part has the instructions that go on the label. And 3^rd part tells the quantity to be dispensed.