A student appears for tests I, II and III. He will be successful if he passes through either Test I and Test II or Test I and Test III. The probability of a student passing the tests I, II, III are p. q, $$\frac{1}{2}$$ respectively. If the probability that a student is successful is $$\frac{1}{2}$$, then which one of the following is true?

A

$$p = q = \frac{1}{2}$$

B

$$p = 1, q = \frac{1}{2}$$

C

$$p = \frac{1}{2}, q = 1$$

D

$$p = \frac{1}{2}, q = \frac{1}{4}$$