If 9/(1 + 4/x) = 1, then x =  Choose the correct choice from the following options.
A) 3
B) 1 / 2
C) 1 / 3
D) - 1 / 3
E) - 3

Rationale: "the expression 9 / ( 1 + 4 / x ) = 1 should have been equal to something . if 9 / ( 1 + 4 / x ) = 1 = 1 = > 9 x / ( x + 4 ) = 1 = > 9 x = x + 4 = > 8 x = 4 = > x = 1 / 2 correct option : b"
Answer: B