Which of the following sentences correctly replaces repeated nouns with pronouns?

a) Jacob told her what he was thinking, but Molly didn't know what Jacob was talking about.
b) Jacob told Molly what Jacob was thinking, but she didn't know what Jacob was talking about.
c) Jacob told Molly what he was thinking, but she didn't know what he was talking about.
d) He told her what he was thinking, but she didn't know what he was talking about.