[amp_mcq option1=”27″ option2=”35″ option3=”18″ option4=”9″ correct=”option1″]
The odd number in the given set is $\boxed{35}$. All other numbers are perfect squares.
A perfect square is a number that can be obtained by squaring an integer. In other words, it is a number of the form $n^2$, where $n$ is an integer.
The numbers $9$, $18$, and $27$ are all perfect squares, since they can be obtained by squaring the integers $3$, $2$, and $3$, respectively. However, $35$ is not a perfect square, since it cannot be obtained by squaring any integer.