Part B has an error. The base form of the verb 'watch' should be used in place of 'watched', as the modal verbs ('should' in this sentence) are always followed by a verb in its base form. Hence, (c) is the correct answer.
Note: Modal verb: A verb used with another verb to express an idea such as possibility that is not expressed by the main verb. The modal verbs in English are "can," "could," "may," "might," "must," "ought," "shall," "should," "will," and "would." They do not change their form (spelling) and they have no infinitive or participle (past/present). Example: I can speak Spanish. Here 'can' expresses the ability of the person to speak (main verb) Spanish. This ability cannot be expressed by the main verb 'speak'.
Study Notes
Category
