Option 1: Grievance -> A complaint or cause for complaint, similar to grouse which means to complain.
Option 2: Plaudits -> Means praise or approval, opposite of grouse.
Option 3: Conceit -> Refers to excessive pride or vanity, unrelated to complaining.
Option 4: Endorsement -> Means support or approval, opposite of grouse.
Hence, Option 1: Grievance -> "Grouse" means to complain or grumble, and "grievance" is a formal complaint or grounds for complaint, making them synonymous -> correct