Convert from direct speech to indirect speech: Nitin said to his brother, "What a beautiful painting it is?"

The original sentence is an exclamatory sentence expressing admiration. In indirect speech, exclamatory sentences are introduced with verbs like 'exclaimed' or 'wondered'. The tense changes from present ('is') to past ('was'), and the exclamatory structure 'What a beautiful painting' is converted into a statement. Option (b) correctly conveys the wonder/admiration that Nitin expressed, with proper tense change.