Option B is the correct answer. The subject of the sentence is in the singular, so the following verb will also be in the singular. Moreover, the sentence seems to be in the present perfect tense. Thus, an auxiliary verb in the present tense followed by the past participle is appropriate, as given in Option B. Options  A and D are in the plural form. Option C, despite ring in the present tense and in singular form, is not compatible with the present participle in the sentence. Thus, Options A,C and D are all incorrect.