--4000 gold ,silver and pottery artifacts were found .
--When was ______exactly?
--It was on December 22nd, 2007 _______ the Nanhai No.1 , the sunken ship ,was raised from the seabed .
A. it , that B. one , when C. that ,that D. it , when

确实让人头晕，我在yahoo上问外国的朋友应该如何选择，结果各种答案都有，随便摘几个给你看

1
.I am pretty sure it's D.
Since the 3rd line starts out with it, the answer above has to be it. So, it's either A or D. Then, it explains the event. So, the next one has to be when.


2.
The correct answer is C: that, that.

When was that exactly -- this refers to the previous sentence and an event. So it requires "that" not "it."
Most Americans would get this wrong, too. So, I wouldn't worry too much about this particular construction.
8 hours ago
Source(s):
I'm a writer and editor.

3.
"When was it exactly?" is correct, but "When was that exactly?" is also correct.
"it" and "that" refer to the time of the discovery, and the question is the same as asking "When was the discovery exactly?"

"It was on December 22, 2007 that the Nanhai No. 1, the sunken ship was raised from the seabed." is correct.
Sometimes you might hear someone say "It was on December 22, 2007 when the Nanhai No. 1, the sunken ship, was raised from the seabed.", but most people will say "that" and not "when".

所以说，这个题目也许根本就是存在多种答案的，或者出题人按自己的意思出题，这个题本来就是有问题的。还有可能是在语法上只有一个答案正确，但是实际应用中，大家却可以有多种说法，毕竟口语和严格的语法有区别。而且，连美国人也混淆的问题，对于我们这些英语学习者来说，根本不用在乎这么高深的东西