依次填入下面一段文字横线处的语句，衔接最恰当的一组是眼睛的构造非常精巧。眼睛的主要部分是眼球，眼球壁分为外、中、内三层。外层由角膜、巩膜组成，内层是视网膜。________，________，________。________，________，________。这些信号被大脑转换成图像，我们就可以看见东西了。①视网膜上含有对光线极为敏感的细胞②它们就向大脑发出信号③当光线照射到这些细胞上时④物体的光线通过角膜进入眼睛内⑤由晶状体把这些光线汇聚在视网膜上⑥然后通过眼睛内的瞳孔

We promise that we will never forget the human _______. We all love to live in peace.

The thief was brought in, his hands ____________ behind his back [ ]

The head teacher said we had only three days to finish the project.–Don’t worry. We have already ______ two third of it.

You ____be tired—you have worked only for ten minutes．