The administration is trying to preempt Obamacare sticker shock in 2015 by pleading with Americans to shop around in the marketplaces instead of automatically re-enrolling in the health plans they chose last year. Officials said Thursday those who don’t look around and compare plans during open enrollment could see their costs rise because the so-called benchmark plans are more expensive this year.But the Health and Human Services Department said there are more insurers offering more plans this year, meaning that in most states consumers can choose from three or more issuers. And HHS said those options mean most consumers who...