Answer:
B. Doctor Rank's admission of love prolongs the suspense because now Nora cannot ask him for help.
The passage that the question was missing:
Read the excerpt from act 2 of A Doll's House.
Rank: [leaning towards her] Nora—do you think he is the only one—?
Nora: [with a slight start] The only one—?
Rank: The only one who would gladly give his life for your sake.
Nora: [sadly] Is that it?
Rank: I was determined you should know it before I went away, and there will never be a better opportunity than this. Now you know it, Nora. And now you know, too, that you can trust me as you would trust no one else.
Nora: [rises, deliberately and quietly] Let me pass.
Rank: [makes room for her to pass him, but sits still] Nora!
Nora: [at the hall door] Helen, bring in the lamp. [Goes over to the stove.] Dear Doctor Rank, that was really horrid of you.
Rank: To have loved you as much as anyone else does? Was that horrid?
Nora: No, but to go and tell me so. There was really no need—
Rank: What do you mean? Did you know—? [MAID enters with lamp, puts it down on the table, and goes out.] Nora—Mrs. Helmer—tell me, had you any idea of this?
Nora: Oh, how do I know whether I had or whether I hadn't? I really can't tell you—To think you could be so clumsy, Doctor Rank! We were getting on so nicely.
Rank: Well, at all events you know now that you can command me, body and soul. So won't you speak out?
Nora: [looking at him] After what happened?