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 （ ）瓦莱里在《人与贝壳》一文中说：“无知是一种无价之宝， 。你随意翻阅一部字典或编撰一部辞书，便会发现每一个字都遮掩着一个无底洞。”①有的人则由于不知如何利用它而任意荒废，②然而绝大多数人却将它任意处置，③我们应该在那些自认为最了解的领域内探索自己的无知，④这真是天大的错误，⑤有的人通过学习破坏了它，⑥人们本应珍惜它的一点一滴，

There is no reason why you shouldn’t tell theheadmaster _________ that you are resigning because he has arranged your post.

Another newest man-made satellite is the earth now．

One of our rules is that every student ______wearschool uniform while at school.

Linda’s father isn’t an engineer. Hermother isn’t an engineer, ______ .