Name: Martin

From: London

Class: Class 2, Mr Smith's class

Favourite animal: dogs

I've got a black dog and I do sports with it near my home.

Name: Lisa

From: New York

Class: Class 1, Mrs King's class

Favourite animal: cats

I've got a brown cat and I play with it at home.

Name: Lu Jin

From: Hangzhou

Class: Class 3, Mr Wang's class

Favourite animal: tigers

I've got many tiger pictures and there are two pictures on the wall.

Name: Song Yuan

From: Haikou

Class: Class 4, Mrs Li's class

Favourite animal: pandas

I've got many panda pictures and I go to see pandas in the zoo on Saturday.

运用数据进行分析是历史学习的一种重要方法。导致下表1921—1925年苏联（苏俄）粮食产量变化的主要原因是(     )

苏联（苏俄）粮食产量变化表

下列解释有误的一项是（   )