单选题 ______ the calculation is right, scientists can never be sure that they have included all variables and modeled them accurately.
【正确答案】 A
【答案解析】[解析] 句意：即使计算正确，科学家们也不敢肯定他们已包括了所有的变量并精确地模拟了这些变量。even if(即使)表示让步。从该句前后部分的语义关系看，需要填入的成分应该表达让步的关系。