汉代，“丝綢和香料从其原产地中国和亚洲东南部向西运输到达中亚、伊朗和罗马帝国°”这反映了当时（    ）

两位同学用不同的显微镜，甲用“10×”的目镜和“10×”物镜进行观察，乙用“16×”的目镜和“40×”的物镜进行观察，其中____ 同学所看到的细胞体积大，____ 同学所看到的细胞数目多．

A : What's your favourite invention?

B : Of course computers. They are very important in people's life now.       

A: I like computers, too. I think they will be used even more widely in the future.

B: I agree with you.        

A: I usually use my computer for looking up information reading books and playing games;

B: Do you like shopping online?

A : Yes, of course.       

B: That's true. However, sometimes it isn't safe to buy things online.

A: Yes, so we should be careful when shopping online. What do you like to do with your computer?

B:        

A: You must have many net friends.

B: Sure. I have about 10 friends who are from different countries.

A:        

若将实验药品改为镁条，反应结束后降至室温，观察到水倒吸入集气瓶大于1/5。根据资料信息，小明知道镁条可以与空气中的氮气、二氧化碳发生反应，进而影响反应结果。镁条与氮气反应可以生成氮化镁（Mg3N2）和碳，请写出相应的化学方程式      。