The correct answer is $\boxed{\text{A}}$.
The sum of the three interior angles of any triangle is always equal to 180 degrees. This is known as the Triangle Sum Theorem. Therefore, for a well-conditioned triangle, no angle should be less than 20 degrees, because if any angle were less than 20 degrees, the sum of the three angles would be less than 180 degrees, and the triangle would not be a valid triangle.
Option B is incorrect because 30 degrees is the measure of one of the acute angles in a 30-60-90 right triangle. A well-conditioned triangle can be a right triangle, but it does not have to be.
Option C is incorrect because 45 degrees is the measure of one of the acute angles in a 45-45-90 right triangle. A well-conditioned triangle can be a right triangle, but
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