A student received an ""A"" on the first test of the semester. The student wants to calculate the probability of scoring an ""A"" on the second test. Historically, the instructor knows that the joint probability of scoring ""A""'s on the first two tests is 0.5. Also, historically, the probability that a student scores an ""A"" on the second test given that a student scored an ""A"" on the first test is 0.9. What is the probability that a student will score an ""A"" on the second test?
A) 0.50
B) 0.95
C) 0.55
D) 0.90