两个语法题请教？？

jeff2003

1。In geometry, an ellipse may be defined as the locus of all points_____distances from
two fixed points is constant.
A. which as the sum of;       B. of the sum which;   
C.whose sum of whose;       D.whose sum that the.
答案给的是C，水妖的语法上选B.哪位大侠给解释一下？

2。The piano is (a) stringed musical (instrument) in which the (strings) are strike, by felt-covered (hammers controlled) by a keyboard.
答案选C,很不明白？？

多谢了！！

困难是弹簧

1、请参与这里的讨论
http://forum.chasedream.com/dispbbs.asp?BoardID=19&replyID=72918&id=10780&star=1&skin=0

困难是弹簧

第2题没看出C有错啊

redpassion

是stirke 错了八
改过去分词吧~~

yongchou

十成(not just 八)是mistakenly underlined.
Redpassion is right.
(strike)--> struck