Hi there! The answer is C.
An irrational number is a number that cannot be written as a fraction.
A, B and D can be written as a fraction.
A. 3.5 = 3 1 / 2
B. square root of 36 = 6 = 6 / 1
D. 37 / 100 is already a fraction.
Hence, the only number that cannot be written as a fraction is the square root of 48.

The answer is C: the square root of 48 is an irrational number.