请教 provided/if 区别

solome

161. A wildlife expert predicts that the reintroduction of the caribou into northern
Minnesota would fail if the density of the timber wolf population in that region is
more numerous than one wolf for every 39 square miles.

A.would fail if the density of the timber wolf population in that region is more numerous than
B.would fail provided the density of the timber wolf population in that region is more than
C.should fail if the timber wolf density in that region was greater than
D.will fail if the density of the timber wolf population in that region is greater than
E.will fail if the timber wolf density in that region were more numerous than

我对此题的选择没有疑问，我想问privided 和if 的区别。
OG 上给出了一句话是B uses the pretentious and illogical word provided for if in a
conditional clause after a negative idea (would fail).
似乎是说provided  不能用在一个a negative idea 上，我查了一下朗文，给出的解释是：
if and only if

请教一下具体的用法

yzlinlin

我倒觉得这题provided & if 的区别不是主流，而是1，时态；2，无that.

不过，综合该句的意思，的确if 要比if and only if 要合适-----怎么感觉考逻辑似的。WHATEVER，也不奇怪，GMAT考试无论是阅读，语法都时不时在测验考生的逻辑思维能力，更甭说逻辑本身了。

gemj

LDOCE
PROVIDED
used to say that something will only be possible if something else happens or is done
synonym providing
He can come with us, provided he pays for his own meals.
There's no annual fee provided that you use the credit card at least six times a year.

Cambridge Learner's Dictionary
provided (that)
only if
He's welcome to come along, provided that he behaves himself.

剑桥国际英语词典（CIDE）的解释是：
if, or only if
Provided (that) there are no objections, we will begin with item three on the agenda.
He says he'll go parachuting provided/providing (that) you do too.

SOED
provided
On the condition, supposition, or understanding that, or that; it being stipulated or arranged that or that.
Allowed to talk..provided that they did not raise their voices.   
M. Keane Jane did not mind expense provided she got what she wanted.
（注：He was released on bail on condition that he did not go within half a mile of his mother’s address. On the condition表达的明显是必要条件。）

总结：虽然有些词典也认为其有IF的含义，但大多数还是认可且只认可作only if解。而only if的意思是“只有”，表达的是必要条件（上面所有的例子我们当作必要条件来理解都不会出现荒谬的意思）。相反IF表达的是充分条件。这两个词的区别是不是主要在这里？
至于OG 上说的：B uses the pretentious and illogical word provided for if in a conditional clause after a negative idea (would fail).
是不是说这里用必要条件不合适？
第二个例子前面就是否定的意思。

solome

谢谢yzlinlin：）

更谢谢gemj gg，so多的解释呢。我想gg说的是对的，provided 是必要条件，if是充分条
件。我刚刚又想了想OG的解释，觉得或者它的重点并没有落在a negative idea 上，它只
是在陈述事实-条件从句是跟在这个后面，它对provided的解释实际上是落在the
pretentious and illogical word 上，这个应该也是传达了gg说的意思。

sigh...看来偶的阅读没有过关呢。

hodgechen

问题深度见功利，我差的太远了，差的FAR FAR 啊，第一个做副词修饰第二个形容词

Shuaishuai

GEMJ解释的比ETS更到位！非常感谢！

littlemuddie

哦，原来 provided 有此含义。真是高人。

还是要好好学习。

luxinwinter

duo xie

ethyl

不顶不是我性格~~

sammaijgd

明白了