Answer:
Amazing
Explanation:
Definition of Amazing: causing great surprise or wonder; astonishing.
Definition of Astonishing: extremely surprising or impressive; amazing.
Synonyms for Astonishing:
amazing<<< only choice
astounding
bewildering
breathtaking
extraordinary
impressive
marvelous
miraculous
Wouldn't the subject be I because it is about you?
The compound verb is earned good grades.