In order for a regular polygon to tile a plane, the interior angle must be a divisor of 360°. The interior angle at each vertex will have measure 180(n -2)/n for an n-sided polygon. So you must have
.. 360/(180(n -2)/n) is an integer
.. = 360n/(180(n -2))
.. = 2 +4/(n -2)
That is, n-2 must be a divisor of 4, one of 1, 2, 4. So, the number of sides of the regular polygon must be 3, 4, 6.
Of your choices, A and D are appropriate.
