Correct Answer:
C. xlsx
.xlsx is the standard file extension for Microsoft Excel workbooks since Office 2007. Options like .msxcl and .xcl are incorrect, while .xlsm is specifically for macro-enabled workbooks, not the general extension.
.xlsx is the standard file extension for Microsoft Excel workbooks since Office 2007. Options like .msxcl and .xcl are incorrect, while .xlsm is specifically for macro-enabled workbooks, not the general extension.