阅读理解。

     This is a book. It's an English book. It is my English book. That is a

dictionary. Is it Lucy's dictionary? No, it isn't. It's Tom's dictionary. Her

dictionary is in her bag. Look! What are these? They're pens. Are they

Tom's pens? No, they aren't. They are Mike's.

1. What's this? It's _______________.

2. What's that? It's _______________.

3. Is it Tom's dictionary? _______________.

4. Where is her dictionary? ______________.

5. Whose pens are those? ________________.

下列现象中，最能说明植物生长素低浓度促进生长，高浓度抑制生长“两重性”的是（）

A．茎的向光性和负向重力性

B．顶端优势

C．扦插枝条生根

D．无子果实的形成