Which of the Following Is TRUE of the Open Stage

Multiple Choice

Which of the following is TRUE of the open stage of a midlatitude cyclone in the Northern Hemisphere?

A) The lifting mechanism is completely cut off from the warm air mass.
B) A disturbance develops along the polar front with warm air converging and rising near the surface.
C) The faster moving cold front overtakes the slower warm front and wedges beneath it.
D) Warm air moves northward along an advancing front,while cold air advances southward.