Your Answer is

Correct Answer is B

Explanation

Because ABCD is a rhombus, ABCD is symmetrical about the diagonal, so ∠BAD = ∠DAC = m°. And because AB is parallel to CD, ∠BAD = ∠ACD = m°, so ∠CDE = ∠DAC + ∠ACD = 2m°, so choose B