Which of the following fractions is in its lowest terms?

Correct option is B

Concept Used:

A fraction is in lowest terms if HCF (GCD) of numerator and denominator = 1

Solution:

Option A: $$\frac{28}{79}$$​​

79 is a prime number

79 does not divide 28

HCF = 1 

fraction is in lowest term.

Option B: $$\frac{31}{186}$$​​

186 = 31 × 6

HCF = 31

fraction is not in lowest term.

Option C:  $$\frac{9}{156}$$​​

9 = 3 × 3, 156 = 3 × 52

HCF = 3

fraction is not in lowest term.

Option D: $$\frac{57}{152}$$​​

57 = 3 × 19, 152 = 8 ×19

HCF = 19

fraction is not in lowest term.

Thus, option(A) is correct.