The formula for computing impedance in a series circuit containing resistance, capacitance, and inductance is __________. [ NOTE: the symbol * stands for 'multiplied by' ]

A.Z = RT + XL + XC
B.Z = R + XL - XC
C.Z * Z = R * R + (XL - XC) * (XL - XC)
D. Z = R * R + (XL * XC) - (XL * XC)