[求助]关于GWD-13-11答案的疑问

A South American bird that forages for winged termites and other small insects while swinging upside down form the foliage of tall trees, the graveteiro belongs to the ovenbird family, a group of New World tropical birds that includes more than 230 species and that are represented in virtually every kind of habitat.

B.      graveteiro belongs to the ovenbird family, a group of New World
                    tropical birds that includes more than 230 species and  is

C.      graveteiro belongs to the ovenbird family, a group of New World
                    tropical birds that include more than 230 species and  is

D.      graveteiro, which belongs to the ovenbird family, a group of New World tropical birds that includes more than 230 species and that are

E.       graveteiro, which belongs to the ovenbird family, a group of New World tropical birds that includes more than 230 species and is

答案是B

看了答案，我整理了一下答这题的思路：

首先includes是a group的主语，用单数；其次，从
                    is/are的选择上只有is对，不管是和belongs并列还是和includes并列。如此排除A，C，D下来，只剩B和E。

而E在and之前句子不完整，缺谓语，所以只有B是正确的。虽然我不清楚B中的is是与belongs并列还是与includes并列。

我的疑问是：如果是与includes并列，它之前应该有that才能构成平行结构；如果是和belongs并列，那同位语a group of New World
                                tropical birds that includes more than 230 species 应该做插入语，and之前应该有逗号与它分隔开。

真搞不懂啊，有nn帮忙解释一下吗？

A South American bird that forages for winged
termites and other small insects while swinging upside down form the foliage of
tall trees, the graveteiro (S) belongs  to the ovenbird family, a group (同位語) of New World tropical birds  that includes more than 230
species and that are represented in
virtually every kind of habitat.

A.     
graveteiro
belongs to the ovenbird family, a group of New World
            tropical birds that
includes more than 230 species and that are

B.      
graveteiro
belongs to the ovenbird family, a group of New World
            tropical birds that includes more than 230 species
and is

C.     
graveteiro
belongs to the ovenbird family, a group of New World
            tropical birds that include more than 230
species and is

D.     
graveteiro,
which belongs to the ovenbird family, a group of
New World tropical birds that includes more
than 230 species and that are

E.      
graveteiro,
which belongs to the ovenbird family, a group of New World
tropical birds that includes more than 230 species and is (graveteiro作為S時,缺verb)

A錯在主詞是a group時，跟that 子句使用的
            are 不一致

C錯在主詞是a group時，include動詞時態不對

D錯在a group 跟
            are 不一致

E錯在graveteiro之後句子不完整，缺動詞.

A South American bird that forages for winged
termites and other small insects while swinging upside down form the foliage of
tall trees, the graveteiro (S) belongs  to the ovenbird family, a group (同位語) of New World tropical birds  that includes more than 230
species and that are represented in
virtually every kind of habitat.

A.     
graveteiro
belongs to the ovenbird family, a group of New World
            tropical birds that
includes more than 230 species and that are

B.      
graveteiro
belongs to the ovenbird family, a group of New World
            tropical birds that includes more than 230 species
and is

C.     
graveteiro
belongs to the ovenbird family, a group of New World
            tropical birds that include more than 230
species and is

D.     
graveteiro,
which belongs to the ovenbird family, a group of
New World tropical birds that includes more
than 230 species and that are

E.      
graveteiro,
which belongs to the ovenbird family, a group of New World
tropical birds that includes more than 230 species and is (graveteiro作為S時,缺verb)

A錯在主詞是a group時，跟that 子句使用的
            are 不一致

C錯在主詞是a group時，include動詞時態不對

D錯在a group 跟
            are 不一致

E錯在graveteiro之後句子不完整，缺動詞.

为什么C不对？

我认为
        ：

1，that 前的birds是复数，后面的include也应该是复数才对？！

2，而且a group of也是代表“好几个人组成的”意思，也应该用复数啊？