下列与有机物的结构、性质有关的叙述正确的是（　　）

若实数x，y满足$\left\{\begin{array}{c}x+y-1\ge 0\\ x-y-2\le 0\\ y\le 1\end{array}\right.$，则z=﹣$\frac{1}{3}$x+y的最小值为____ 

下列有关实验的叙述，正确的是（    ）

阅读理解What are the children doing?
    What are you doing, children? Oh, we are playing games. Look at Li Lei. He is throwing the frisby with Jim. What about the twins? They are flying kites. The kites are very nice. One like a bird, the other is like a plane. Li Tao is playing basketball with me. Han Mei and Ma Lin are singing an English song under a big tree.

写出钟面时间．

____