请英语高手们帮我区别一下下面的两题~感激不尽啦~

请英语高手们帮我区别一下下面的两题~感激不尽啦~
1.Beijing sold 154200 new cars in the first half of 2011,___ is 224200 fewer than the same period in 2010.
A.what B.that C.whose D.which A
2.Accepting the award on the stage was an amazing moment,__ he would never forget.
A.which B.what C.one D.it
第一题为什么不选which呢？第二题为什么不选which呢？既然第一题选了what,那么第二题为什么不能选what或者是which呢？

其实,第一题会不会是答案错了呢.
个人觉得选D which
就是典型的非限制性定语从句,which指代前面说到的所卖出的汽车数量,比2010年同时期的要少了224200.
网上搜了一下,看到有新闻的原文（链接发不上,直接弄过来）
>Car sales drop in Beijing
北京半年少卖22万辆车
Beijing sold 154,200 new cars in the first half of 2011,which is 224,200 fewer than the same period in 2010 and shows a 59.2% year-on-year decrease,according to data released Thursday by China Association of Automobile Manufacturers and Beijing Yayuncun Car Trade Market,the Beijing Times reported.The trade volume of 2nd-hand cars hit 122,600 in the first 6 months of 2011,which dropped by 46% from the same period in 2010.Beijing’s policy on limiting the purchases of cars and the adjustment on personal income tax threshold exclude 90% of non-permanent residents in Beijing from the group of potential car buyers.
据《京华时报》报道,中汽协、亚运村汽车交易市场等14日联合发布数据显示,今年上半年,北京市累计交易新车154200辆,比去年同期少卖了224200辆,同比降幅达59.2%；二手车累计成交122600辆,同比减少了46%.限购新政及个税起征点调整将使90%的外地在京人员无缘在京购车.
2.这里的one是同位语 一般 one= a/ an +n.
这题目的 one= an amazing moment
Accepting the award on the stage was an amazing moment,one that/ which he would never forget.=Accepting the award on the stage was an amazing moment,one he would never forget.
上台领奖是一个让人激动的时刻,一个他将永远都难忘的时刻.
one 是同位语,表示的是“这个时刻”,后面再加了个定语从句来修饰这个时刻,“他将永远难忘的时刻”.因为在定语从句中,one充当的是宾语,所以引导词which/that可以省略掉,变成了题目中的Accepting the award on the stage was an amazing moment,one he would never forget.
which 个人觉得,从语法上来说也是行的,但是当表示非限制性定语从句时,这题目的which容易引起歧义,可以是表示这个moment,可以是表示上台领奖这件事情,而用同位语one,它表示的是moment的同位语,因此就很明确是说这个moment,是最佳的答案.
再问： 嗯嗯~那么这样说来，可不可以理解为第一题的which既可以指代前面的一整个句子，也可指154200这个数字，为了避免歧义，就用what来代指154200，并且引导这个句子呢？