Persuade is a synonym of Convince. Convince is a synonym of Assure. Assure is a different concept from Trouble. Trouble is a type of Pregnancy. 
Tough is a synonym of Dense. Dense is the opposite of Intelligent. Intelligent is similar to Bright. Bright is a synonym of Promising. 
Persuade <--Synonym--> Convince <--Synonym--> Assure <--DistinctFrom--> Trouble --IsA--> Pregnancy 
Tough <--Synonym--> Dense <--Antonym--> Intelligent <--SimilarTo--> Bright <--Synonym--> Promising 