Identify the polarity of end D and describe the direction of magnetic field lines between the magnets.

I)
The plotting compass needle's North pole (indicated by the arrow) points towards end B and away from end C. This means that end B is a South pole (attracting the North pole of the compass) and end C is a North pole (repelling the North pole of the compass). Since C is the North pole of the right-hand magnet, its opposite end, D, must be the South pole.

The polarity of end D is:

II)
The magnetic field lines emerge from the North pole and enter the South pole. Since C is a North pole and B is a South pole, the magnetic field lines will originate from C and terminate at B. The lines should be drawn as curved paths with arrows pointing from C to B.

(Please imagine the following drawing on the diagram provided in the question)

      A       B <--- (South Pole)
      +-------+
              |
              |  <-- Magnetic field lines with arrows pointing from C to B
              |
      +-------+
      C (North Pole)  D <--- (South Pole)

(Note: I cannot draw directly on the image. The field lines should be drawn as curves originating from C and ending at B, with arrows indicating the direction from C to B.)