Please please explain why that answer is correct and why i got it wrong!

How does drinking alcohol or using drugs put a person at risk for hiv infection? a.they improve judgment, which makes it more likely for people to engage in risky behavior. b.they impair judgment, which makes it more likely for people to engage in risky behavior. c.they impair judgment, which makes it less likely for people to engage in risky behavior. d.they improve judgment, which makes it less likely for people to engage in risky behavior.