Concept:The idiom “It's all Greek to me” means a person cannot understand something at all.
Explanation:The word “Greek” is used here to represent a language that is completely unknown to the speaker.
So, when someone says “It's all Greek to me,” they are saying the subject is totally incomprehensible.
Now, check each option with this meaning.
Option A says “It is foreign to me,” which is too vague and not exactly about the inability to understand.
Option B says “It appears classical to me,” which does not connect to the idiom's actual meaning.
Option C says “I can't understand it at all,” which directly matches the idea of total unintelligibility.
Option D adds an emotion like frustration, but the idiom does not necessarily express frustration.
Therefore, the correct choice is the one that states a complete lack of understanding.
Answer:I can't understand it at all.