Horror flick “Paranormal Activity 4” opened atop the North American box office this weekend, while political thriller “Argo” held onto second place, industry figures showed Monday. The fourth installment in the found-footage franchise raked in $29 million to lead the top 10, while several other pre-Halloween spooky movies also did well, according to box office tracker Exhibitor Relations. Ben Affleck’s “Argo,” which earned $16.4 million, tells the true story of how a CIA agent managed to rescue six Americans who had escaped the embassy in Tehran in 1979 and taken shelter at the Canadian ambassador’s residence. Last week’s top earner “Taken 2” — Liam Neeson’s return as ex-CIA agent Bryan Mills — was pushed down to the number three spot, earning $13.3 million in its third weekend. In fourth place was animated comedy “Hotel Transylvania,” in which monsters become Dracula’s guests, with $13 million in ticket sales.