Match the following:

Let us match each concept in the left column with its corresponding phase/technique in the right column:

1. P. Lexical analysis $\rightarrow$ 2. DFA minimization: Lexical analyzers use Deterministic Finite Automata (DFAs) to recognize tokens. Minimizing DFAs produces efficient tokenizers.

2. Q. Parsing $\rightarrow$ 4. Production tree: Parsing involves constructing a parse tree (or production tree) from a grammar to verify the syntax of the input string.

3. R. Register allocation $\rightarrow$ 1. Graph coloring: Register allocation is mapped to the graph coloring problem (an NP-complete problem) on an interference graph to assign registers to variables.

4. S. Expression evaluation $\rightarrow$ 3. Post-order traversal: Evaluating an expression represented as an abstract syntax tree / expression tree is done using post-order traversal (evaluating sub-expressions before applying the operator).

Thus, the correct matching is P-2, Q-4, R-1, S-3, which corresponds to option (C).