[单选] More has been learned since 1945 about the chemical changes in the body than in all human hist

题目：[单选] More has been learned since 1945 about the chemical changes in the body than in all human hist
A . in
B . that
C . which
D . the

正确答案：B
解析：
这里指的是在1945年之前的那个时期，并有强调之意。选项B是正确的。【句子大意】自从1945年以来，我们对人体化学变化的了解比1945年之前的整个人类历史所了解的还要多。