2004 AMC 10B Problem 6

Which of the following numbers is a perfect square?

\mathrm{(A) \ } 98! \cdot 99! \qquad \mathrm{(B) \ } 98! \cdot 100! \qquad \mathrm{(C) \ } 99! \cdot 100! \qquad \mathrm{(D) \ } 99! \cdot 101! \qquad \mathrm{(E) \ } 100! \cdot 101!

Full credit goes to MAA for authoring these problems. These problems were taken on the AOPS website.