三道OG上的SAT语法题In Germany,foresters discovered that trees kille

三道OG上的SAT语法题
In Germany,foresters discovered that trees killed by acid rain had begun to die four years (earlier,even though the trees had shown no signs of disease them)
n.
D earlier without any signs of disease shown then
这个题答案选A,不知道D为什么错.
test 3,section 6,18
(As) children mature,they develop (an independence) that their parents,who (have been) responsible for them since they were born,often find difficult (to accept).(No error)
为什么用an independence不用independences
Test3 Section10 5
The Poetry Book Society is an organization in London that (provides information and guidance for all lovers of contemporary poetry and giving them discounts on books of poetry.)
C not only provides information and guidance for lovers of contemporary poetry and were giving discounts on books of poetry
B provides information,guidance,and the getting of discounts on books of contemporary poetry
可是C里面的they会不会指代不明?按照句子结构的话they应该指information and guidance吧.觉得B也挺对的