Eventually, the narrator is "enabled to see the extent and aspect of the prison" by A) "the sweep of the pendulum."
B) “a wild sulphurous luster."
C) "the vapor of heated iron."
D) "familiar faces in coals that glow."​

B “a wild sulphurous luster

Explanation:

from the political point of view it could be said that the candidate   is an effective speaker because she takes a strong position on the issue. it is an open discussion but probably she is making a presentation and can choose which subjects she wants to address. she is very likely to attain her aim which is to convince voters to accept her proposal.