A bottom-up parser that analyzes the input from left to right and constructs a rightmost derivation in reverse is known as an:

• A. LR Parsers
• B. LL Parsers
• C. Recursive Descent
• D. Shift-Reduce Parsers

Answer: (A)

In bottom-up parsing, the parser moves from the input tokens toward the start symbol. The description here fits LR parsers: they read the input from left to right and, by performing shifts and reductions on a stack, generate the rightmost derivation in reverse. As each reduction replaces a recognized handle with its left-hand side nonterminal, the sequence of reductions traces out the rightmost derivation backward. This left-to-right, reverse-rightmost-derivation behavior is what defines LR parsing. LL parsers, in contrast, operate top-down and build a leftmost derivation, while recursive descent is a top-down method using procedure calls. Shift-reduce describes the general mechanism of bottom-up parsing, but the specific property of constructing a rightmost derivation in reverse aligns with LR parsing.