Which of the following is not a valid data type in Excel?
A. Number
B. Character
C. Label
D. Date/Time

B. Character is the wrong answer.

C. The label is the correct answer.

Because the Character is nothing but the TEXT data type whereas the Label is not available in Excel.

Agreed. The label is the correct answer. Neither Character or Label are examples of number format in the excel 2019 I use.