如果实数x，y满足$\left\{\begin{array}{c}x-4y+3\le 0\\ 3x+5y-25\le 0\\ x\ge 1\end{array}\begin{array}{c}\\ \end{array}\right.$，目标函数z=kx+y的最大值为12，最小值为3，那么实数k的值为(     )

可逆反应N₂+3H₂⇌2NH₃的正、逆反应速率可用各反应物或生成物浓度的变化来表示．下列各关系中能说明反应已达到平衡状态的是（   ）

句型转换 
(1)There are some vegetables for dinner. （改为否定句）
There ____ vegetables for dinner.
(2)How's the weather in Beijing. (同义句转换)
____ the weather____ in Beijing.
(3)The students are having an English class . （对画线部分提问）
____ are the students ____ ?
(4)Your brother has a great time playing computer games. (同义句转换)
Your brother has ____ computer games.
(5) No photos here. (同义句)
____  any photos here.