but it has never had so much meaning as it (a)did/was on a stage in great britain, being sung by a mobile phone salesman named paul potts.

답 : as it did - 앞에서 반복되는 동사가 be동사가 아닌 일반동사(had)라서 did를 쓴 것?

potts is an average-looking man (b)his/whose teeth are not straight.

답 : whose - 한 문장에 동사가 두개니 관계대명사가 필요함?

but that does not mean we haven’t made an impact, changed lives for the better, or (c)had/have a meaningful life on this planet. find your inner paul potts. everyone has one.

답 : had - changed(과거)와 함께 연결되는 구문이니 과거동사?