= Solution
B contains both $-\mathrm{CH_2-CH(Cl)}-$ and $-\mathrm{CH_2-CH(OCOCH_3)}-$ monomeric units distributed along the same <carbon> backbone: \b[a <vinyl chloride-vinyl acetate copolymer>]. One possible local segment is
$$
\mathrm{\cdots-CH_2-CH(Cl)-CH_2-CH(OAc)-CH_2-CH(Cl)-\cdots},
\qquad \mathrm{OAc=OC(O)CH_3}.
$$
The ester is attached through <oxygen> to the backbone <carbon>. A <random copolymer> should not be drawn as two long homopolymer blocks. The stated $75:25$ <monomer> feed is not enough to prove an incorporated $75:25$ unit ratio: <monomer> reactivity ratios and conversion affect composition and sequence statistics. Under an explicitly ideal equal-incorporation assumption that ratio could be used as a schematic average, not a periodic repeat.
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