Find the odd number from the alternatives given below. Three numbers are perfect squares, while one is not a perfect square. Identify the odd one out. (A) 16 (B) 4 (C) 2 (D) 36 (E) 81

Introduction / Context:
This odd-one-out question checks the concept of perfect squares. A perfect square is a number that can be written as n*n for an integer n. The odd number will be the one that cannot be expressed in that form, while the others can.

Given Data / Assumptions:

• Perfect square means: number = n*n for some integer n.
• We verify by matching the number to known squares (2^2, 3^2, 4^2, etc.).
• If one option is not a square while others are, it is the odd one out.

Concept / Approach:
Identify which numbers are squares of integers. If 4 out of 5 are perfect squares and one is not, the non-square is the odd option.

Step-by-Step Solution:

Verification / Alternative check:
You can also check by bounding: 1^2 = 1 and 2^2 = 4. Since 2 lies between 1 and 4 and is not equal to either, it cannot be a perfect square. This confirms that 2 is the odd number in the group.

Why Other Options Are Wrong:

Common Pitfalls:
Some students confuse 'even numbers' with 'perfect squares' and assume all even numbers are squares, which is false. Another pitfall is checking only the last digit: while squares often end in 0,1,4,5,6,9, that alone is not sufficient to prove squareness. Always confirm with an exact integer multiplication or bounding between consecutive squares.

Final Answer:
2