Answer is C.
Since in overlay we use the memory location to run large files. For example if there is a two pass assembler which needs 150 kB of memory bt we have 100kb then the assembler has two phases i.e one phase needs 70kb then other needs 80kb say then for one pass we will assign 70kb of memory after it is completed then other 80kb of memory for 2nd pass this way we run a large program.
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