Select the correct phase portrait for the following system of differential equations:

$$\dot x_1 = 2x_1 x_2,\qquad \dot x_2 = x_1 2x_2.$$

Select the correct phase portrait for the following system of differential equations:

$$\dot x_1 = -x_1 3x_2,\qquad \dot x_2 = 2x_1 4x_2.$$

Select the correct phase portrait for the following system of differential equations:

$$\dot x_1 = x_1 x_2,\qquad \dot x_2 = -x_1 x_2.$$