Electrophilic aromatic sulfonation of benzene gives which major product?

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Electrophilic aromatic substitution is the key process here: the benzene ring reacts with a strong sulfonating agent to attach a sulfonyl group directly to the ring. In fuming sulfuric acid, sulfur trioxide acts as the electrophile (SO3+). The ring donates electrons to SO3+, forming a sigma complex, and then a proton is removed to restore aromaticity, giving benzenesulfonic acid (the ring bears an -SO3H substituent directly attached to it). This product is a sulfonic acid substituent, not an ester of sulfuric acid; the sulfonyl group attaches via sulfur to the ring, not through an oxygen bridge. So the major product is benzenesulfonic acid. The other options come from different reactions: nitration would yield nitrobenzene; oxidation or carboxylation would give benzoic acid; forming a sulfuric acid ester would require a phenol to form an aryl sulfate, which isn’t the result of straightforward benzene sulfonation.