Refer to figure.
Note: This question is a newly updated version of question 718479 with a different question image.

The figure depicts the effect of mountain waves.

Mountain waves are oscillations to the lee side (downwind) of high ground resulting from the disturbance in the horizontal air flow caused by the high ground. This results in significant pitching oscillations and down drafts.

Looking at the answers:

Possibility of clear ice directly above the waves --> INCORRECT. Despite wandering into the Meteorology syllabus, clear air icing is not a feature of mountain waves.

You need to avoid the low side of the wave as the updraft may be so strong that the aircraft is not able to maintain the planned descent path --> INCORRECT. Behind the lee of the mountain is an area of down drafts as the air sinks down with the terrain. Excessive updraft is exactly the opposite of the problem encountered.

The mass and balance limits maybe be exceeded --> INCORRECT. Mountain waves will no effect on the mass and balance of the aircraft, despite the pitching oscillations, if the load is properly secured.

You need to avoid the low side of the wave as the downdraft may exceed your aircraft's rate of climb capability --> CORRECT. On the lee side of the terrain, the aircraft could encounter very strong down drafts. It is certainly possible that the air is descending more quickly than the aircraft can climb.