Refer to figures.
Pressure patterns in the atmosphere dictate the movement of air, the wind; high and low pressure is self-explanatory, in a low pressure area, there is less air, so less force acting upon objects. The laws of thermodynamics like equilibrium, and therefore high pressure always tries to flow to low pressure to equalise the two. This is called the pressure gradient force, and forms the wind direction, along with the coriolis force.

The coriolis force is that which causes air to turn right in the Northern Hemisphere, due to the different rotational speeds of the Earth's surface. It means that air will end up following the isobars on a pressure chart, perpendicular to the pressure gradient force.

This makes it very difficult for high pressure to flow to low pressure, as it gets turned away from its path as soon as it starts moving. There is, however, some air that manages to escape a high pressure zone, and some air which enters a low pressure zone. This mostly happens near the surface, where the friction effects of the surface reduce the coriolis force, and the pressure gradient force can do more.

The outflow of air from a high is called divergence. For air to flow outwards near the surface, the air has to come from somewhere, and it arrives from above, travelling down inside the high pressure zone. This creates clear weather conditions with a high chance of inversion after a few days.

The inflow of air into a low is called convergence. As the air comes together, it has to travel somewhere, and it is forced upwards, which causes uplift and creates clouds, and therefore weather.

In this question, they are asking about the atmospheric divergence, assumably from a high pressure zone. As mentioned above, this is where some air is able to travel across the isobars and away from the high pressure area, towards the low. This means that there is a component of the wind that is blowing perpendicular to the isobars, and this is the component of divergence.

The options mention the friction layer. The friction layer is a layer of air above the ground, within which the wind is affected by friction with the surface, also called the boundary layer. Inside this layer, the air is slowed down more by friction, and the coriolis force is therefore not as strong, so some divergence/convergence can occur. The options mentioning it are not correct though.