In part (a), the subject is "The voice", which is a singular noun. The phrase, 'of sanity and patriotism' acts as an adjective for the said noun. Hence, the verb which follows should agree with the singular noun and also be in singular form. However, in part (b) the word, 'are' is the plural form of the word, 'be'. The singular form of the verb 'be' is: 'is'. Hence, part (b) is incorrect.

The correct sentence is: '(a) The voice of sanity and patriotism (b) is important (c) to dispel the prevalent confusion'. Hence, option B is the correct answer and options A and C are incorrect.

Option D is incorrect as part (b) contains an error.