How did Mendel's experiments challenge the idea of blending of traits?

Correct answer: A hidden trait appeared again in the second generation.

The blending theory suggested that parental traits would permanently mix, like two colours of paint, so a recessive trait should not reappear unchanged. In Mendel’s pea experiments, a trait absent in the first hybrid generation reappeared in the second generation, such as dwarfness after crossing tall plants. This showed that hereditary factors remain distinct and can separate into later offspring. Hence option A is correct.