Answer: (iii) Reverse of a rightmost derivation

Explanation

A bottom-up (shift-reduce) parser starts from the input string and repeatedly reduces a handle to a non-terminal until the start symbol is reached.

Each reduction undoes one step of a rightmost derivation, so the sequence of reductions is a rightmost derivation traced backwards.

Example for $E \to E+E \mid id$ on $id + id$:

• Rightmost derivation: $E \Rightarrow E+E \Rightarrow E+id \Rightarrow id+id$
• Reductions performed by the parser: $id+id \to E+id \to E+E \to E$ (exactly the reverse).

(Top-down parsers build a leftmost derivation; options (i), (ii), (iv) are wrong.)

$$\boxed{\text{(iii) Reverse of a rightmost derivation}}$$