If $a, b, c, d$ are four consecutive natural numbers, which of the following is a perfect square?

Question

Accepted Answer

$abcd + 1$

Answer

$abcd$

Answer

$ab + cd$

Answer

$abcd - 1$

If a,b,c,da, b, c, da,b,c,d are four consecutive natural numbers, which of the following is a perfect square?