BY的语法，真不知道怎么判断了

白勇语法 看得非常头大，第五章分词和不定式里面，14题很是强调介词+ing分词在句尾的逻辑主语判断，好不容易把这点记在脑子里，第15题却说介词+ing分词在句首必须判定逻辑主语，但在句尾就不用判断逻辑主语。

听说不少人都看这本书，我也使劲看，是学到些东西，但是碰到这种问题到底要如何取舍

谢谢

能不能把题贴上来一起讨论，有时要具体问题具体分析

14--Alaska rgularly deposits some of its profits from the sale of oil into a special fund,with the intention to sustain the state's economy after the exhaustion of its oil reserves.

A.fund,with the intention to sustain the state's economy after the exhaustion of its oil reserves.

B.fund, the intention of which is to sustain the state's economy after they have exhausted their oil reserves.

C.fund intended to sustain the state's economy after oil reserves are exhausted.

D.fund intended to sustain the state's economy after exhausting its oil reserves.

E.fund that they intend to sustain the state's economy after oil reserves are exhausted.

15--In assessing the problems faced by rural migrant workers, the question of whether they are better off materially than the urban working poor is irrelevant.

A.In assessing the problems faced by rural migrant workers, the question of whether they are better off materially than the urban working poor is irrelevant.

B.The question of whether the rural migrant worker is better off materially than the urban working poor is irrelevant in assessing the problems that they face.

C.A question that is irrelevant in assessing the problems that rural migrant workers face is whether they are better off materially than the urban working poor.

D.In an assessment of the problems faced by rural migrant workers, the question of whether they are better off materially than the urban working poor is irrelevant.

E.The question of whether the rural migrant worker is better off materially than the urban working poor is irrelevant in an assessment of the problems that they face.

14题强调逻辑主语判断是在区别干扰项，

15题是在强调prep+-ing phrase在句尾的两种可能性，即逻辑主语为主句主语，或和所修饰v.同主语，所以说要回避这个问题，避免引起歧义。这里说不用判断，可能有两个含义1, 歧义错了，不用费时间判断；2 B已由明显的代词无指代（they cannot refer to the worker)排除了，不用再考虑。

我在找分词的用法，刚好翻到他这，同讨论一下。

3. prep+ 宾语，这里宾语noun phrase 优于-ing, 即不需要有逻辑关系，或者逻辑不能合理建立( 如15题，the question 和 in assessing的逻辑关系是怎么也不能建立的，question不可能是assess的动作发出者）， 这个时候也不用判断。用prep+noun( in an assessment of..)消除了这个逻辑错误。