关于英语单选问题：

首先答案为C，因为What是一个非限定性疑问句，是对Difficulty的性质来提问的，所以复数形式的Difficulty是不成立的，有谁听说过what books do you want？ 难道用单数就一定要用what a difficulty 这样是一样的感叹句，所以这里是单数，是就他的性质提问。
在说she has to learn 这个定语从句。这里省略了一个that，全句应该是Difficulty that she has to learn . 可能这里你to learn你搞不清楚，to learn 是形容DIFFICULTY的，这里是个介词短语做difficulty的定语。你就可以看成是一个形容词。
为什么你说的不行，因为IN这样是不能省的，还有没有什么has in learning something这样的句子，如果把has 改成IS in 应该没问题。
如果句子你要表示的是She has difficulty in learning..In决对不能省，而且这句话意义错的，To 表将要了解的困难，你这里是表正在知道的困难，所以完全不行。

选D. Difficulty不可数。Learning用Ing是因为它前面省略了介词In，Difficulty在句子里是先行代词而不是宾语， 所以She的前面省略了That。

希望你看懂了。

It will be partly cloudy.多云
It will be mainly clear.晴到多云
It will start cloudy and turning overcast a bit later.多云转阴
It will start cloudy and breaking up clear.多云转晴
There will be thunder shower.雷阵雨
There will be drizzle.毛毛雨
There will be light rain to moderate rain.雨量小到中等
In the day,the high will be 19 degrees and the low will be 9 degrees.最高温度是19摄氏度,最低温度是9摄氏度

1.she knows no matter what _______,as long as she doesn't give up,she will succeed sooner or later.
B.difficulties she has learning

因为选它

1.she knows no matter what _______,as long as she doesn't give up,she will succeed sooner or later.
A.difficulties she has to learn