Chelsea Clinton was confronted at a book signing with a question about her father’s alleged marital infidelity. Appearing at an Austin, Texas book signing Friday to promote her children’s book “It’s Your World: Get Informed, Get Inspired & Get Going,” Clinton was caught off guard by camera-toting conservative activist Robert Morrow. “I am so proud to be my parents’ daughter,” Clinton said after Morrow asked about longstanding but unconfirmed rumors that Chelsea was the offspring of an affair between her mother and her mother’s onetime law partner Webster Hubbell. Morrow then asked whether Clinton’s father targets young girls for sex....