形如$\left|\begin{array}{cc}a& c\\ b& d\end{array}\right|$式子叫作二阶行列式，它的运算法则用公式表示为$\left|\begin{array}{cc}a& c\\ b& d\end{array}\right|$=ad﹣bc，依此法则计算$\left|\begin{array}{cc}2& 1\\ -3& -4\end{array}\right|$的结果为（　　）

完形填空。

    A boy and a girl catch a bird and 1 it in a birdcage (鸟笼）. They like it 2 and 3 it every day. A cat sees the bird and wants 4 her supper. 5 the bird is in the cage. She can't catch it. So she is very 6.

    One day, she opens the door of the cage 7 wants to catch it. But the bird flies away. The cat 8, and she has 9. The two children 10 and　see the bird isn't in. They are very angry and put the cat into the cage.

如果将细胞比做汽车，那么细胞中的____相当于发动机，它将细胞中的一些____当做燃料，使之与____结合，经过复杂的变化转变成____和____，同时将有机物中的____释放出来供细胞利用．