As a place that is home to 131 species of fish，the Cahaba River is flowing for 190 miles through the heart of Alabama。AAs a place that is home to 131 species of fish，the Cahaba River is flowing for 190 miles through the heart of Alabama。Bhome

As a place that is home to 131 species of fish，the Cahaba River is flowing for 190 miles through the heart of Alabama。AAs a place that is home to 131 species of fish，the Cahaba River is flowing for 190 miles through the heart of Alabama。Bhome
As a place that is home to 131 species of fish，the Cahaba River is flowing for 190 miles through the heart of Alabama。
A
As a place that is home to 131 species of fish，the Cahaba River is flowing for 190 miles through the heart of Alabama。
B
home to 131 species of fish,the Cahaba River flows
选B 为什么？我选的A

As a place that is home to 131 species of fish，the Cahaba River is flowing for 190 miles through the heart of Alabama。AAs a place that is home to 131 species of fish，the Cahaba River is flowing for 190 miles through the heart of Alabama。Bhome
1.首先从时态的角度来看,“河往阿拉巴马流”是一个具体客观的现象,用一般现在时表示,没有必要用现在进行时
2.从简洁性角度考虑,既然as sth.和sth.直接作同位语语法上面都没错,干嘛要as的结构；更关键的是a place that is这几个词就算删掉也不会产生任何影响,SAT的语法题遵循写作原则,而写作原则中就有一条叫做Omit needless words（见The elements of style）者不单单是体现在冗词上,还体现在“一个句子里面的每一个词都应该有其独特、不可取代、不可删除的意义”,既然a place that is不存在“不可替代、不可删除性”,当然就是啰嗦了

能把大题的题目要求发过来吗？

描述的是客观事实，所以要用现在时，而不用正在进行时。