When using vlookup, the is optional?

To  VLOOKUP function in excel has 4 arguments:
1. the lookup_value -the value you are looking for
2. table_array - The range of cells that make up the table
3.column_index-he number of the column from which to retrieve a result (column_index)
4. range_lookup - The match mode - this argument is optional
When using vlookup, the range_lookup argument is optional

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