A grammar that produces more than one parse tree for some sentence iscalled ____ a) Ambiguous b) Unambiguous c) Regular d) None of the mentioned

The correct answer to the question is a) Ambiguous.

Explanation

In formal language theory, a grammar is said to be ambiguous if there exists at least one string (sentence) that can be generated by the grammar in multiple ways, resulting in more than one parse tree. This means that the same sentence can be interpreted in different ways based on the different structures represented by these parse trees. Ambiguity can lead to confusion in understanding the meaning of the sentences produced by such grammars. On the contrary, a grammar that produces only one parse tree per sentence is referred to as unambiguous. Regular grammars, on the other hand, follow specific constraints that typically do not allow for ambiguity, but the term "regular" itself does not define ambiguity directly like "ambiguous" does.

In summary, the presence of multiple parse trees for a single sentence indicates ambiguity in the grammar, making option a) Ambiguous the correct choice.