Carrot is a type of Reward. Reward is related to Degree. Degree is related to Achievement. 
Excellent is a synonym of Crucial. Crucial is a synonym of Essential. Essential is related to Necessary. 
Carrot --IsA--> Reward <--RelatedTo--> Degree <--RelatedTo--> Achievement 
Excellent <--Synonym--> Crucial <--Synonym--> Essential <--RelatedTo--> Necessary 