※ 引述《amysky0205 (=Amy=)》之銘言：
: In order to withstand tidal currents, juvenile horseshoe crabs frequently
: burrow in the sand. Such burrowing discourages barnacles from clinging to
: their shells. When fully grown, however, the crabs can readily withstand
: tidal currents without burrowing, and thus they acquire substantial
: populations of barnacles. Surprisingly, in areas where tidal currents are
: very weak, juvenile horseshoe crabs are found not to have significant
: barnacle populations, even though they seldom burrow.
: Which of the following, if true, most helps to explain the surprising finding?
: (A) Tidal currents do not themselves dislodge barnacles from the shells of
: horseshoe crabs.
: (B) Barnacles most readily attach themselves to horseshoe crabs in areas
: where tidal currents are weakest.
: (C) The strength of the tidal currents in a given location varies widely over
: the course of a day.
: (D) A very large barnacle population can significantly decrease the ability
: of a horseshoe crab to find food.
: (E) Until they are fully grown, horseshoe crabs shed their shells and grow
: new ones several times a year.
: OA: E
: Crabs don't burrow----> substantial populations of barnacles.
: BUT
: In areas where tidal is weak and thus crabs seldom burrow, barnacles
: population isn't significant.
: (A) tidal currents沒有將baracles逐出crabs的殼--->沒有解釋為何在weak tidal的地區
: barnacals沒有這麼多
: (B) 說barnacles在tidal weakest的地區容易附著在crabs上--->這樣應該有比較多
: barnacles才對!
: (C) 說tidal currents的stregth----Irrelevant
: 想請問(D)和正確選項(E)
: (D)不行是因為 說如果barnacles的人口很大會使crab找食物的能力下降
: ---> 並沒有解釋crab seldom burrow為何barnacles的人口還是很少
: 請問這樣的思路對嗎?
: 謝謝!!!!
如果說加強/削弱/前提/評估 題型是要抓準結論句的話，
那麼沒有結論的解釋題型就是要抓準矛盾點（也就是「令人不解的現象」）來解題。
這題的矛盾點是：
Surprisingly, in areas where tidal currents are very weak, juvenile horseshoe
crabs are found not to have significant barnacle populations, even though
they seldom burrow.
「在浪潮弱的情況下，年輕的螃蟹身上沒有barnacle（儘管不burrow）」
D選項只說了當barnacle 變多的時候會怎樣，
可是並沒有把它連結到矛盾句，
也就是說「barnacle多」跟「浪潮弱」完全是兩碼子事，
之間沒有連結，無法互相解釋。
比如矛盾句若是「馬英九愚昧，為何總統能一直作下去」
選項說「當高捷男在捷運上蓋外套時，他是在____」
兩者完全是兩碼子事阿兩碼子事。
Dustin
--
Dustin Deng
(一戰自修760，AWA 5.5)
若有GMAT問題需要諮詢，
詳細解題及考試策略：
http://dustingmat.blogspot.tw/
--
※ 發信站: 批踢踢實業坊(ptt.cc)
◆ From: 116.59.242.56