Which of the following is correct?
I came across this sentence when reading the NY Mag; the writer produced sentence A.
A: It’s also a real biological feature, a specialized bundle of cells that regulates our cyclical processes.
B: It’s also a real biological feature, a specialized bundle of cells that regulate our cyclical processes.
I guess the question boils down to what noun "that" refers to. When I was looking through a grammar book yesterday, the author specifically mentions that relative pronouns like that and which refer to the first noun/pronoun before, which should be "cells" instead of "bundle", making B correct