PREP 求解？

麦兜woo

The rate of a certain chemical reaction is directly proportional to the square of the concentration of chemical A present and inversely proportional to the concentration of chemical B present. If the concentration of chemical B is incresed by 100percent, which of the following is the closest to the percent change in the concentration of chemical A required to keep the reaction rate  unchanged?

A. 100%percent decrease
B. 50%decrease
C.40%decrease
D. 40%increase
E. 50%increase

答案选D， 谁能帮忙解释下这道题什么意思，怎么做，题目都看不懂，越详细越好，O(∩_∩)O谢谢

语法：
The Achaemenid empire of Persin reached the Indus Vally in the fifth century BC, bringing the Aramdic script with it, from which was derived both northern and southern India alphabets.

A. the Aramdic script with it, from which was derived both nothern and
b. the Aramdic script with it, and from which was derived both nothern and the
C. with it the Aramdic script, from which derive both the northern and the
D. with it the Aramdic script, from which derives both northern and
E. with it the Aramdic script, and deriving from it both the northern and

答案选C， 怎么来的？