Let the amount of water added / litre of spirit = x

So now new volume of the mixture = 1 + x

Given S.P. of the mixture = Rs 75 per litre

Hence total S.P. = 75(1+x)

Whereas C.P. = 60 [ As no cost for water mentioned ]

Hence profit = 75 + 75x - 60 = 75x + 15

Hence profit percentage = (Profit / C.P) * 100 = [15(5x + 1) / 60] * 100

Given profit percentage = 37.5 %

Hence we have ,

[15(5x + 1) / 60] * 100 = 37.50

==> (5x + 1) / 4 = 0.375

==> 5x + 1 = 1.50

==> x = 0.1

Hence for each litre of spirit , 0.1 litre of water is added to get the desired mixture.

**Hence the ratio of spirit to water in the mixture = 1 : 0.1 = 10 : 1**

** Hence B) should be the correct answer.**