jjEMm‖Select All
PDEFv‖Selects the entire content of the current file, frame, or text object.
YDU8D‖To select all of the cells on a sheet, click the button at the intersection of the column and row header in the top left corner of the sheet.
eCfyi‖Choose .
gXMsj‖
G7z8T‖ + A
JWfov‖To select all of the sheets in a spreadsheet file, right-click the name tab of a sheet, and then choose Select All Sheets.