Four persons independently solve a certain problem correctly with probabilities $$\frac{1}{2}, \frac{3}{4}, \frac{1}{4}, \frac{1}{8}.$$ Then the probability that the problem is solved correctly by at least one of them is

A

$$\frac{235}{256}$$

B

$$\frac{21}{256}$$

C

$$\frac{3}{256}$$

D

$$\frac{253}{256}$$