SOAP doesn't define a message exchange pattern
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a. true
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b. false, SOAP is completely a request/response protocol
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c. may be
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d. may not be
SOAP itself doesn't mandate any specific message exchange pattern (MEP). While request/response is common, SOAP supports various patterns including one-way, solicit-response, notification, and peer-to-peer messaging. The protocol is deliberately flexible about MEPs.
SOAP is a messaging protocol/envelope format, and by itself it does not mandate a specific message exchange pattern (MEP) — request/response, one-way, and other patterns can all be layered on top of SOAP depending on the binding (e.g. HTTP). This is why the statement that SOAP doesn't define an MEP is true, even though request/response is a common usage pattern in practice.