13－7＝____。

鉴定可溶性还原糖、蛋白质、脂肪、观察DNA和RNA在细胞中的分布所用实验材料较合理的一组是

用方框所给出的选项完成对话。

A middle school student and her mother are visiting the security education show(安全教育展)

M: Come on, darling, so many pictures here!

S: ____  

M: Traffic safety.

S: Sounds boring.

M: ____ 

S: Maybe. Oh! Mum, look at this picture, a boy is hit a car when he is running across the road. ____ 

M: So it is!

S: ____  That helps us stay safe from danger.

M: Yes, better safe than sorry. Let's go to another hall to learn more about hot to protect ourselves.

S: ____  Let's go.