题目

The cancer death rate in the U.S. fell by the most on record as advances in treatments for lung tumors （肿瘤） like video-assisted surgery helped prolong the lives of patients.The death rate from cancer has been gradually declining for 26 years, thanks in large part to fewer people smoking cigarettes. But from 2016 to 2017, the most recent period available, it dropped by 2.2%, the most ever in a single year, according to a report released Wednesday by the American Cancer Society. That compares with an average 1.5% yearly decline over the decade. The drop translates to roughly 2.9 million 下列关于K和K+性质的叙述中，正确的是：    A、它们都是强还原剂    B、它们的电子层数相同    C、它们都显碱性    D、它们灼烧时都能使火焰呈现紫色（透过蓝色钴玻璃观察）