The correct option is C 18
Using the formula
Mode, Mo=L+f1−f02f1−f0−f2×h
Lower limit of modal class =L=15
Frequency of modal class =f1=30
Frequency of class preceding modal class =f0=15
Frequency of class succeeding modal class =f2=20
Size of class interval =h=5
Substituting the values, we get
Mo=15+30−152×30−15−20×5
=15+3
=18
Thus mode is 18.