两道语法题还是不理解阿,请大家指教

哭哭马路

His studies of ice-polished rocks in his Alpine home-land, far outside the range of present-day glaciers, led Louis Agassiz in 1837 to propose the concept of an age in which great ice sheets had existed in now currently temperate areas.
B.in which great ice sheets existed in what are now temperate areas
D.when great ice sheets existed where there were areas now temperate
正确答案是B，想知道D为什么不对呢 in which 和when不相等吗


According to some analysts, whatever its merits, the proposal to tax away all capital gains on short-term investments would, if enacted, have a disastrous effect on Wall Street trading and employment.
A.its merits, the proposal to tax
E.the proposal's merits are, taxing
正确答案是A,我选了E,

serendipityh

age 后面加in which
in what are now temperate areas 的意思是这个地方曾经不是温带地区, 现在是温带.
E改变句意

yiyun2

2题，E中taxing away all capital gains...的应该是the proposal ，而非proposal's merits。