Final answer:
The Excel formula to sum cells in column A if cell C3 equals 5, and otherwise display a blank, is =IF(C3=5,SUM(A:A),"").
Step-by-step explanation:
The correct answer to the Excel question is A) =IF(C3=5,SUM(A:A),""). This formula checks to see if cell C3 equals 5, and if it does, it sums up all the cells in column A. If C3 does not equal 5, the formula results in a blank cell. The syntax for the IF function in Excel is =IF(logical_test, [value_if_true], [value_if_false]), where logical_test is the condition you want to test, value_if_true is the value that is displayed if the condition is true, and value_if_false is the value that is displayed if the condition is false. In this case, value_if_false is an empty string ("") which displays a blank cell.