Plastic is related to Balloon. Balloon is related to Rubber. Rubber is related to Bath. Bath is related to Morning. 
Proud is the opposite of Modest. Modest is related to Decent. Decent is the opposite of Sad. Sad is a synonym of Low. 
Plastic <--RelatedTo--> Balloon <--RelatedTo--> Rubber <--RelatedTo--> Bath <--RelatedTo--> Morning 
Proud <--Antonym--> Modest <--RelatedTo--> Decent <--Antonym--> Sad <--Synonym--> Low 