大全-section 13-2 困惑中

2.                 Judge Lois Forer’s study asks why do some litigants have a preferred status over others in the use of a public resource, the courts, which in theory are available to all but in fact are unequally distributed among rich and poor.

(A) do some litigants have a preferred status over others in the use of a public resource, the courts, which in theory are available to all but in fact are unequally distributed among

(B) some litigants have a preferred status over others in the use of a public resource, the courts, which in theory are available to all but in fact are unequally distributed between

(C) do some litigants have a preferred status over another in the use of a public resource, the courts, in theory available to all but in fact are unequally distributed among

(D) some litigants have a preferred status to another in the use of a public resource, the courts, in theory available to all but in fact not equally distributed between（B）

(E) does one litigant have a preferred status over the other in the use of a public resource, the courts, in theory available to all but in fact they are not equally distributed among

答案是B，这个没什么疑问，我的问题是：

1.    怎么理解     some litigants have a preferred status over others in the use of a public resource, the courts, which in theory are available to all but in fact are unequally distributed between

黑体部分的语法作用，是同位语吗？还是插入成分，如果是后者which clause 是不是应该看成修饰a public resource, 后面用单数？

2. 假如加上such as the courts, 就应该用单数 Is available 吧？