Count by tens write the number name.

The correct answer is: Forty

Here, we have to count by 10s and write the number name of the result.
Count by 10s
10, 20, 30, 40
Number is 40.
40 when written in words is forty.
Hence, the correct option is A.

There are many ways of representing a number such as number name, binary system, roman numerals, etc.