They are called compound sentences.When 2 sentences are connected.
Sorry if there are any words misspelled. I hope this helps :)
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"
