选择合适的选项补全对话。

A. Can I have a dog? B. They are really useful. C. They are dogs. D. What can they do? E. They can help blind people, too.

Sam: What are these, Mum?

Mum:

They are very clever.

Sam:

Mum: They can help the firefighters.

Sam: Oh!

Mum: Yes, they are.

Sam:

Mum: Yes, you can.

Sam: Great!