根据句意写出括号内所给单词的适当形式。

小题1:Can you tell me the time of his _______ (arrive)? I can meet him at the station.

小题2:These little children can’t look after _________ (them).

小题3:I left my home town ten years ago. Now I am glad to see the _________ (develop) of it.

小题4:It’s _____________ (honest) to tell such a lie. It will make your friends unhappy.

小题5:We will hold a party to celebrate Lucy’s __________ (twenty) birthday.

2010年1月澳大利亚研究人员开发出被称为第五形态的固体碳，这种新的碳结构称作“纳米泡沫”，它外形类似海绵，比重极小，并具有磁性。纳米泡沫碳与金刚石的关系是[ ]

A．同种物质

B．同分异构体

C．同位素

D．同素异形体