The correct answer is: C. are
The verb “to be blamed” is a transitive verb, which means that it requires a direct object. In this case, the direct object is “Sita or her brothers.” The verb “to be blamed” is also in the plural form, which means that the subject must also be in the plural form. Therefore, the correct answer is “C. are.”
The other options are incorrect because they are not in the plural form. Option A, “is,” is in the singular form. Option B, “has,” is in the singular form and does not agree with the direct object. Option D, “was,” is in the past tense and does not agree with the present tense of the sentence.
In conclusion, the correct answer to the question “Sita or her brothers . . . . . . . . to be blamed” is “C. are.”