Assume that x is a char variable has been declared and already given a value. write an expression whose value is true if and only if x is an hexadecimal (base 16) digit (0-9 plus a-f or a-f).

F. a fair coin is thrown in the air four times. if the coin lands with the head up on the first three tosses, what is the probability that the coin will land with the head up on the fourth toss? a. 0 b. 1/16 c. 1/8 d. 1/2