下列有关我国西北地区的描述，正确的是（　　）

    John gets up early from Monday to Saturday, because he must go to school before 7:30 on weekdays(工作日) and go to Drawing Club at 8:00 on Saturday mornings. He usually goes to the bookshop on Saturday afternoon, and after dinner he watches TV until(直到) midnight(午夜).

    He doesn't get up early on Sundays. John's parents both work on Sundays. John always watches TV after he gets up. Then he usually goes to KFC to have a hamburger and some juice for lunch. After that, he goes back home and starts to play computer games until his parents come back. He does his homework after dinner. He usually has lots of weekend homework, so he must spend three hours on it. He usually goes to bed at about 11:00 p.m. on Sundays. He often complains(抱怨) he has too much homework to do.

根据短文内容，选择最佳答案。

$\{\begin{array}{c}2x-7<3\left(x-1\right)①\\ 5-\frac{1}{2}\left(x+4\right)\ge x②\end{array}$

中央电视台“幸运52”栏目中的“百宝箱”互动环节，是一种竞猜游戏，游戏规则如下：在20个商标中，有5个商标牌的背面注明了一定的奖金额，其余商标的背面是一张苦脸，若翻到它就不得奖．参加这个游戏的观众有三次翻牌的机会．某观众前两次翻牌均得若干奖金，如果翻过的牌不能再翻，那么这位观众第三次翻牌获奖的概率是（       ）