The given statement is a saying or a proverb.
Option A: 'Need' as a modal refers to an obligation or a necessity. It is generally used in negative or interrogative sentences, in the form 'need not be'. Hence this word isn't appropriate here; option A is incorrect.
Option B: 'Dare' denotes a threat and means 'be challenged to do something'. It does not relate to the given sentence, proverbs are not threats. Hence B is incorrect.
Options C and D: 'Must' and 'should' have similar meanings.
'Should' is the past tense of 'shall'. It refers to a piece of advice, a recommendation, it is used to suggest to a person what to do.
'Must' talks about an obligation or a necessity to do something. It is a stronger word as compared to 'should'. It is used to tell someone what he 'has to do'. It's not a piece of advice but an obligation.
The given proverb means 'if one cannot solve a problem, he has to live with it.'
Hence, 'must' is a more suitable modal.
So, option C is correct, D is incorrect.