在2011.5与它的倒数之间有a个整数,在2011.5与它的相反数之间有b个整数,求（a-b)除以（a+b）的值

SAT语法求解 2011.5真题
3.In the Bay of Fundy the rising tide produces a so powerful inward surge that it actually reverses the normal flows of several rivers.
(A)a so powerful inward surge
(B)a powerful inward surge; so
(C)an inward surge so powerful
(D)an inward surge,it is so powerful
(E)so powerful of an inward surge
这题有点糊涂,A不对是因为so不能形容名词吧,但是选C的话不该是 so powerful an inward surge 我当时做的时候觉得应该把powerful改成powerfully…………
14.If not for bees,which are responsible for pollinating the vast majority of Earth’s flowers,many plants were unable to produce fruits or seeds.No error
这个是were改成are吗?
15.From his smile it was evident that Burton had successfully reached an agreement to be averting a strike.
to be averting怎么改?
16.Many people agree that the full artistic potential of jazz was first realized in recordings made by Louis Armstrong with the band known as the Hot Fire.
这题为什么没错呢,agree难道不该改成过去时吗?
17.Had I known that we would be walking the fifteen blocks from the movie theater to the restaurant,I would of worn more comfortable shoes.
这题of改成什么?我觉得改成have,虚拟语气吧
19.In 1961 Rita Moreno gained fame and won an Academy Award for her portraying Anita in the film adaptation of the groundbreaking Broadway musical West Side Story.
for her portraying 改成什么?
20.According to a recent study,the domestication of cats had began in the Middle East over 100,000 years ago.
这个就把began改成begun就行了吗?还是改成现在完成时?
为什么over 100,000 years 后面还有个ago呢?

愁死我了.
是这样的,我们住一个宿舍的现在要交电费了,看看每个人是要交多少钱...
用电期间：2011.3.8至2011.5.7 .61天；电量165度；金额一共112.2元..
A,B,C三人一直都住在这里的,D是5月3号走的之前也一直在这里,E是4月21号来的至今...X是4月12号来的至今,大概也可以,看看每个人要交多少钱!

已知函数f（x）是定义在R上的奇函数，且f（x）的图象关于x=1对称，当0≤x≤1时，f（x）=x，那么f（2011.5）=______．

SAT语法2011.5
Henry Wadsworth Longfellow was a descendant of John and Priscilla Alden,（ whose romance he celebrated in the narrative poem the courtship of miles standish.）
这个答案我知道
但是为什么 having celebrated their romance 不对?
答案就是括号里那个