Liam needs to count the cells in the range B1:B20 that contain numbers, dates, or text.Which of the following formulas should he use?

A) '=COUNT(B1:B20)
B) =COUNTA(B1:B20)
C) =SUM(B1:B20)
D) =CALCULATE(B1:B20)

The COUNTA function counts all cells in a given range that are not empty, including those containing numbers, dates, or text. Therefore, B is the best choice for Liam to count all cells in the range B1:B20 that contain numbers, dates, or text.

All other options are not appropriate for the task at hand. Option A would only count cells that contain numbers, while option C would give the sum of the cells' values, not the number of cells that contain any data. Option D is not a valid function in Excel.