What change needs to be made to sentence 7 (reproduced below) to make the sentence grammatically correct?

"It describes how her parents, they had moved to New York from Puerto Rico in the 1940s, found low-paying but steady jobs and an apartment in a local housing project."

a) Remove the comma after "parents."
b) Replace "they" with "who."
c) Change "they had moved" to "having moved."
d) Change "low-paying but steady jobs" to "steady but low-paying jobs."