The correct answer is (c) 4900.
To calculate the sum of all two-digit numbers, we can use the following formula:
$S = \frac{(100 + 99)}{2} \times 99 = 4900$
where $S$ is the sum of all two-digit numbers.
The first term in the formula is the sum of the first and last two-digit numbers, 100 and 99. The second term is the number of two-digit numbers, which is 99.
We can also calculate the sum of all two-digit numbers by adding up all the two-digit numbers from 10 to 99. This gives us the following:
$10 + 11 + 12 + … + 98 + 99 = 4900$
Therefore, the sum of all two-digit numbers is 4900.
Option (a) is incorrect because it is the sum of all one-digit numbers. Option (b) is incorrect because it is the sum of all two-digit numbers from 10 to 99 inclusive. Option (d) is incorrect because it is the sum of all two-digit numbers from 11 to 99 inclusive.