再问那道reasoning！！HELP

lihaolan

12. In the Centerville Botanical Gardens, all tulip trees are older than any maples. A majority, but not all, of the garden's sycamores are older than any of its maples. All the garden's maples are older than any of its dogwoods.
If the statements above are true, which one of the following must also be true of trees in the Centerville Botanical Gardens?
(A) Some dogwoods are as old as the youngest tulip trees.
(B) Some dogwoods are as old as the youngest sycamores.
(C) Some sycamores are not as old as the oldest dogwoods.
(D) Some tulip trees are not as old as the oldest sycamores.
(E) Some sycamores are not as old as the youngest tulip trees.
答案是E。I think c is also right .is that dogwood not tree?

simonshen

T          >   M   > D
S(Maj）> M    >= S（Min）
合并两个公式，可得出 T > M >= S (min)，因此可推出E，Some S （S minority） are   not as old as the youngest T。S（min）最多是跟最老的M一样老，但是所有的T都比最老的M还要老。
C不一定成立。
M > D 和S （maj） > M > = S (Min)   两个条件中，有可能所有的S都比oldest的D更old。比如最年轻的M是5年，D是1-3年不等，而所有的S（min）都是4年的，S（maj）都比5年更老，这个情况符合题意，但所有的S（min）都是4年，所以比oldest的D（3年）更老，而S（maj）肯定比D都要更老，所以所有的S都是older than the oldest D，没有 S 是 not as old as the oldest dogwoods的，因此C不一定成立。不一定成立就是不对的，因为题目问的是must be true。

lihaolan

那不是还有五年的S 和最老的四年的D不一样老么?他不是说some。。如果不是MUST be true .是不是要证明任何的S都和最老的D都一样老。。要不然总有S和最老的D不一样老!!!求助啊！！麻烦了！！

simonshen

哦，我上面最后写错了，我给改一下。
M > D 和S （maj） > M > = S (Min)   两个条件中，有可能所有的S都比oldest的D更old。比如最年轻的M是5年，D是1-3年不等，而所有的S（min）都是4年的，S（maj）都比5年更老，这个情况符合题意，但所有的S（min）都是4年，所以比oldest的D（3年）更老，而S（maj）肯定比D都要更老，所以所有的S都是older than the oldest D，没有 S 是 not as old as the oldest dogwoods的，因此C不一定成立。不一定成立就是不对的，因为题目问的是must be true。

lihaolan

你假设的第二种情况不是也是some M not as old as the oldest D么。。因为所有的M都比D老。。所以不是=some M和最老的D不一样老么。

simonshen

不是，A is not as old as B的意思不是A跟B不一样老，而是A比B小。比如he's not as old as his sister就是他比他姐姐小。如果He's older than his sister,就不能说he's not as old as his sister了。又如，He's not as good as his teacher，意思是他不如他老师，但不能理解为他比他老师强。如果他是比他老师强，better than his teacher,就不能说he's not as good as his teacher。所以如果all S are older than D的话，就不能说是Some S are not as old as D了。

lihaolan

谢了！！我懂了！！！
我理解错英文了。、。