Correct Option: C

Lexical Analyzer uses DFA to recognize the longest possible input sequence that makes up a token. Parser takes input in the form of tokens and usually builds a data structure in the form of parse tree. Here parse tree can be termed as a production tree as parser uses production of the grammar to check whether generated tokens form a meaningful compression. Register allocation can be reduced to K-colouring problem where K is the number of registers available on the target architecture. Post order traversal of expression tree gives postfix notation for a given expression & this post fix notation can be evaluated using stack.