Read the sentence below and answer the following questions stop your incessant whining; it is not going to your cause. use context to determine the meaning of incessant. soft pleasant unending well-founded

Hi! 

Based on context clues, we can tell that the speaker is not enjoying the whining, so we can rule out soft and pleasant. 

Well-founded is an adjective describing a belief or suspicion that a person has as based on facts, saying that whining is well-founded is saying that the whining has a good base or is for a good reason. 

This would make sense, however the speaker says that the whining is not going to help this person's cause, meaning we can rule out well-founded. 

This leaves C. Unending

Hope this helps :)