AIIMS 2018 Chemistry Allotropes Assertion Reason Question

Each of these questions contains two statements, Assertion (A) and Reason (R). Each of these questions also has four alternative choices, only one of which is the correct answer. You have to select one of the codes (a), (b), (c) and (d) given below. Assertion (A) Elementary phosphorus exists in three principal allotropic forms, i.e. white (or yellow), red (or violet) and black. Reason (R) of the three forms, white phosphorus is the most important and most reactive.