Refer to figure.
In normal atmospheric conditions, the air near the ground is warm, and as you climb higher, the air gets progressively colder up to the tropopause. An inversion is the name of the phenomenon when the air actually gets warmer with altitude for a certain layer of the atmosphere.

A ground inversion often occurs on a cold, clear night, and is usually due to the ground cooling very quickly and becoming much colder than the lower layers of air. This cold ground saps the temperature out of the nearby air, cooling it down significantly. Without much wind to mix this air with warmer layers above, the cold air stays close to the ground, and is denser than the warmer air above it, so also wishes to stay lower down. This causes a ground inversion, and is closely related to valley inversions and radiation fog. It is often a very low level inversion, but may span up to 500 ft off the ground in some stronger cases.

The cold air close to the ground is more likely to reach 100% relative humidity and form fog (radiation fog), and as it is cooler that the rest of the air above it, it may drop below 0°C and become supercooled water droplets.

Therefore, a helicopter flying through this layer of air may see some ice accretion.

As for the other options, the wind is usually calm in an inversion like this, no electrostatic discharges would be expected (they are associated with CBs) and the cloud is usually very low within the inversion in the form of radiation fog, closest to the ground where the air is coldest.