A triangle with sidelengths 3, 3 and 3 would be a triangle that has 3 equal sides, that is known as an equilateral triangle which is completely possible.
The usual way to determine if a triangle is possible to build is to find the sum of 2 of its sides and see if it is greater than the other side.
For example, in this case the sum of 3+3 is 6 which is greater than 3, and that's correct for all the other sides.
It means that the correct answer is A. True.