1. The writer directly comments on the personality of the character
2. The personality of the character is directly revealed by the narrator, another character, or the character himself.
3. The writer tells the readers about the character
The first one would be correct.
The subject here is simple" it's just "Antarctica" .
The verb is also not compound, it's a simple verb: "has".
The compound part of the sentence is the object: it is: "a thick ice cover and the highest average elevation of all the continents"
so the correct answer is "compound subject"