GATE CS 2004 Q9 — Parsing (LL, LR)

The correct option is C.

When a program consists of multiple independent source modules (like $M_1$ and $M_2$):

1. Compile Time: Each module is compiled separately into its own object file. During the compilation of $M_1$, the compiler encounters the reference to the function defined in $M_2$. Since $M_2$ is in a different file, the compiler cannot determine its address and leaves it as an unresolved external reference in the object code of $M_1$.
2. Link Time: The linker takes the individual object files of $M_1$ and $M_2$ as input, combines them, and resolves all external references. It matches the function call in $M_1$ with its actual definition in $M_2$, assigning the correct relative addresses.
3. Load Time: The loader places the executable into the main memory for execution, adjusting any absolute addresses if necessary, but the inter-module symbol resolution has already been completed by the linker.

Thus, the reference to a function defined in another module is resolved at Link time.