Bubble is related to Level. Level is a type of Destroy. Destroy is the opposite of Preserve. 
Serious is a synonym of Mean. Mean is a synonym of Indicate. Indicate is a synonym of Argue. Argue is a synonym of Row. 
Bubble <--RelatedTo--> Level --IsA--> Destroy <--Antonym--> Preserve 
Serious <--Synonym--> Mean <--Synonym--> Indicate <--Synonym--> Argue <--Synonym--> Row 