C中的announce to be doing其实结合含义理解一下 会发现这个表达很奇怪
至于prep08语法笔记里说account for 才是正确的搭配...我认为是不对的 on account of+noun同样可以表示原因
A中的问题是时态问题 前面的announce用的是过去式announced，后面的will应该用到的是would

注意：想得有点久了...忽视了them的指代问题

当想用v-ing来修饰之前整个main clause的时候一定要仔细去想一下到底有没有内在的逻辑联系

Ron给的例子感觉也可以解释，信被写的时间和数量超过没有关系。

my brother, who ate bagel bites for breakfast every single day of his high school career, graduated in 1994. --> correct; his eating bagel bites had no impact on his graduation date.
my brother ate bagel bites for breakfast every single day of his high school career, graduating in 1994. --> incorrect; these are two unrelated observations, but this construction erroneously implies some sort of relationship.

Ron给的例子感觉也可以解释，信被写的时间和数量超过没有关系。

my brother, who ate bagel bites for breakfast every single day of his high school career, graduated in 1994. --> correct; his eating bagel bites had no impact on his graduation date.
my brother ate bagel bites for breakfast every single day of his high school career, graduating in 1994. --> incorrect; these are two unrelated observations, but this construction erroneously implies some sort of relationship.

一定要注意逻辑主语的问题...
真正正确的选项的每一点都是（相对）最优的
不管什么时候都一定要关照逻辑主语的问题

这道题可以看作是suggestion，名词和ing的区别吗？

请问一下B appear前面没有连词可以吗？

跟almost的位置也有点关系吧 almost expected almost成修饰 这个动作了

C选项的that从句修饰三者，falls在这路是不是用的不太好啊

通项公式为：an=a1+(n-1)*d。首项a1=21，公差d=2。前n项和公式为：Sn=a1*n+[n*(n-1)*d]/2或Sn=[n*(a1+an)]/2。注意：以上n均属于正整数。

等比数列：an=a1*q^(n-1)，an=q∗ an−1(n>=2,an-1 不等于0，q不等于0),另外注意小数点位置

mark 项数： n=(an-a1)/d[公差]+1 等差数列求和： Sn=(a1+an)*n/2

mark，注意审题， Θ代表的是余数而不是商！

mark，第15高和第20低是同一个商品，所以是15+20-1

mark一下，需要一个一个答案去拆得出最后答案

五分之三是did not survived,审题要仔细。。

审题不仔细。。问的是面积。。

mark，直接代入数字比使用未知数算更加快

Mark，余数