Hi Sagar
The question asked is sum is necessarily , option B will be true only in case of 2 numbers.
You can assume values
$$a_1=2,a_2=3,a_3=6$$
here product is 1 but sum is not 3+1/3.
so option B can be eliminated.

Hi Ashutosh Kumar Singh,
Here, we are first calculating the number of perfect squares that are less than 2018.
The perfect squares are of the form $$1^2,2^2,.....n^2$$
=> $$n^2<2018$$ => n < 44.92 => n = 44.
I hope this helps.