Design equation for varying volume system is ______

• A. t = ( int_0^{XA} frac{dXA}{-rA A} )
• B. t = ( int_0^{XA} frac{dXA}{CA0} )
• C. t = ( int_0^{XA} frac{dXA}{NA0} )
• D. t = CA0 ( int_0^{XA} frac{dXA}{-rA(1+XA A)} )