这道题看了Ron的解释更不明白了，请大家指教

exult1982

The Acoma and Hopi are probably the two oldest surviving Pueblo communities, both dating back at least a thousand years.

A.        both dating
B.        both of which have dated  
C.        and each has dated
D.        and each one dating
E.        each one of which date

答案A

纠结在B和C为什么不能用完成时上。以下是Ron的解释：

Type 1/
If it's a point thing, then "has/have VERBed" means ...
... it happened,
... it's somehow relevant to the present.

E.g.,
People who have graduated from high school usually find employment much more easily than people who have not.
They've graduated (at any time). We don't know when"”maybe yesterday, maybe 40 years ago.
Regardless, it's relevant to the present; we're talking about their job prospects at present.
Type 2/
If it's an ongoing state verb, then "has/have VERBed" without an explicit time period means ...
... it's happened before,
... it's not happening now.

E.g.,
I have lived in Florida.
This implies that I no longer live in Florida. If I still live there now, I'll write I live in Florida.

----- BUT -----

If, for this kind of verb, "has/have VERBed" is used with a time duration, then ...
... it has happened for that duration up to now;
... it may still be happening, or it may just have ended.

E.g.,
I have lived in Florida for twenty years. (written in 2014)
This means I've lived in Florida for the last twenty years (= 1994-2014).
I might still live there.
I may be moving right now.

所以Date属于type1的类型，属于即时的动作。那么整句话意思是这两个民族追溯到了1000年前（到目前为止... it's somehow relevant to the present.），为什么有的解释说：date的现在完成时有潜在含义说"以后都不是追溯到1000年以前了。
糊涂了谢谢！

exult1982

如果与这道题比较的话，同样的date怎么在上一题里就不能用完成时？ 感谢NN指教

Fossils of the arm of a sloth found in Puerto Rico in 1991, and dated at 34 million years old, made it the earliest known mammal of the Greater Antilles islands.

A. sloth found in Puerto Rico in 1991, and dated at 34 million years old, made it the earliest known mammal of
B. sloth, that they found in Puerto Rico in 1991, has been dated at 34 million years old, thus making it the earliest mammal known on
C. sloth that was found in Puerto Rico in 1991, was dated at 34 million years old, making this the earliest known mammal of
D. sloth, found in Puerto Rico in 1991, have been dated at 34 million years old, making the sloth the earliest known mammal on (CORRECT)

Noellee

大家一般在哪里看Ron的解释哇…求指路

大猫超人

完成时强调的是事情做完了，也就是说动作是之前发生的。这道题，明显是表达一个客观的存在事实，属于一般现在时的用法。