each question is either true or false, so the sample space is 2, true and false, two states only.
what's the probability she got one correct, well, the favorable outcomes is 1, possible outcomes is 2, so 1/2.
what's the probability that she got all four correct, we simply multiply the probability of each,
[tex]\bf \cfrac{1}{2}\cdot \cfrac{1}{2}\cdot \cfrac{1}{2}\cdot \cfrac{1}{2}\implies \cfrac{1}{16}\implies 0.0625\qquad or\qquad 6.25\%[/tex]
