根据流动速度场，找出下列流场连续流动的是A. u_x = x^3 sin y, u_y = 3x^2 cos y, u_z = x^3 + y + 2B. u_x = 6(x + y^2), u_y = 2y + z^3, u_z = x + y + 4zC. u_x = y^3 cos x, u_y = x^2 sin yD. u_x = 7x + z^2, u_y = 3y + 2z, u_z = e^x+y+z

A. $u_x = x^3 \sin y$, $u_y = 3x^2 \cos y$, $u_z = x^3 + y + 2$

B. $u_x = 6(x + y^2)$, $u_y = 2y + z^3$, $u_z = x + y + 4z$

C. $u_x = y^3 \cos x$, $u_y = x^2 \sin y$

D. $u_x = 7x + z^2$, $u_y = 3y + 2z$, $u_z = e^{x+y+z}$