Simplify the expression -7x³y√(396x^(5)y^(15)). Which of the following options correctly represents the simplified form of the expression?

A) -7x^(4.5)y^(8.5)
B) -7x^(4.5)y^(10)
C) -7x^(2.5)y^(8.5)
D) -7x^(2.5)y^(10)