Who among the following distinguished the ‘constatives’ from the ‘performatives’?

The correct option is John Austin.

John Langshaw (J. L.) Austin was a prominent 20th-century British philosopher of language who introduced the distinction between "constatives" and "performatives" in his influential lecture series, later published posthumously as the book How to Do Things with Words (1962).

Here is a breakdown of the two concepts he distinguished:
1. Constative Utterances: These are sentences or statements that describe, report, or state a fact about the world. Because they describe a state of affairs, constatives can be evaluated as either true or false. For example, the statement "The sky is blue" is a constative utterance.
2. Performative Utterances: Unlike constatives, performative utterances do not describe or report anything. Instead, the act of speaking the sentence itself performs a specific action. Performatives cannot be described as true or false; rather, they are described as successful (felicitous) or unsuccessful (infelicitous) depending on whether the action was successfully carried out. Examples include: "I promise to help you tomorrow" (performing the act of promising) or "I now pronounce you husband and wife" (performing the act of marriage).

While Austin later refined this distinction into a more comprehensive framework of speech acts (locutionary, illocutionary, and perlocutionary acts), he remains the foundational figure who first separated constatives from performatives.