Answer
C.
Work Step by Step
E. coli and fission yeast are a prokayote and a eukaryote, respectively, so the use/non-use mechanism should relate to this difference. A. and B. are wrong since unicellularity is not useful in differentiating prokaryotes and eukaryotes at the molecular level, and D. can be eliminated because alternative splicing is unrelated to any pause in transcription, which occurs before splicing. C. is correct since it is true and describes a difference between a eukaryote and a prokaryote: the spatial separation of transcription and translation in eukaryotes, unlike prokaryotes.