Sentence Correction (SC) | Re: As a result of surging economic indicators, most analysts

As a result of surging economic indicators, most analysts upgraded the company’s stock to a strong “buy”, ignoring the advice of the head of a watchdog organizationwho warned that the company’s product would prove not only dangerous but ineffective in the long run

(A) who warned that the company’s product would prove not only dangerous but
(B) warning that the company’s product would prove not only dangerous and also
(C) warning that the company’s product would prove itself to