Discourse occurs for information exchange in sentential utterances with information structure (IS). IS needs notions of Topic and Focus, Contrastive Topic (CT) and Contrastive Focus (CF). CT and CF are characterized in question answer conversation. A CT utterance comes from a QUD (Roberts 1996) with a Potential Topic (PT) consisting of a set of relevant alternative members, as a partial answer. Naturally, the question is not completely resolved and invokes a conventional scalar implicature. It is marked by a special intonation or morphemic marker and its implicature is not cancellable, hence conventional. The implicature generated is scalar with respect to the totality or qualitatively, in its DP or predicate PT. CF is argued to invoke a closed set of disjunctive alternative possibilities. An alternative question is licensed if a pair or more of immediately relevant alternatives are available in the discourse context, as in “Will you drink a tea↑ or a coffee↓?” It is semantically strengthened by the restriction “exactly one disjunct holds” (Pruitt & Roelofsen’s 2011) as in Inquisitive Semantics (InqSem). A correction answer is a typical CF: (1) Sue married Sam? Covertly, (2) Did SUECF marry Sam↑ or did RITACF marry Sam↓? (From the immediately relevant alternatives set: {Sue married Sam, Rita married Sam}) (3) No, RITACF married Sam. All CF instances including pseudo-clefts, exhaustive focus, and CF-reduplication have (covert) AltQ. CF and AltQ in disjunction are likewise correlated. A conjunctively conceived CT is distinct from CF, conveying a scalar implicature, due to the unresolved partial information. CF and CT information structure is cognitively real. It is to be explored in terms of proposed possibilities in dynamic exchange.