Question

What is a top-down parser? (a) Begins by hypothesizing a sentence (the symbol S) and successively predicting lower level constituents until individual pre-terminal symbols are written (b) Begins by hypothesizing a sentence (the symbol S) and successively predicting upper level constituents until individual pre-terminal symbols are written (c) Begins by hypothesizing lower level constituents and successively predicting a sentence (the symbol S) (d) Begins by hypothesizing upper level constituents and successively predicting a sentence (the symbol S) Please answer the above question.

Answer 1

Right choice is (a) Begins by hypothesizing a sentence (the symbol S) and successively predicting lower level constituents until individual pre-terminal symbols are written To explain I would say: A top-down parser begins by hypothesizing a sentence (the symbol S) and successively predicting lower level constituents until individual pre-terminal symbols are written.