Derided by critics as everything from unconstitutional to sacrilegious, a proposal to designate the Holy Bible as the state’s official book has nevertheless been approved by lawmakers. Sponsors argue the bill seeks to honor the historical significance of the Bible in Tennessee’s history rather than serving as a government endorsement of religion. But opponents say the measure trivializes the Bible by placing it alongside other Tennessee symbols like the smallmouth bass, the state sport fish; the cave salamander, the state amphibian; and the honeybee, the state agricultural insect. The State Senate approved the bill, 19 to 8, on Monday night, sending it to Gov. Bill Haslam, a Republican, who opposes it but has not said whether he will veto it. The bill’s sponsor, Senator Steve Southerland, a Republican and ordained minister, said a legal organization had offered to defend pro bono any lawsuits challenging it. “So I ask you, what do we have to lose?” he said.