现在小学自然常识课出的题怎么那么难哪!

很多题连我们大人都做不出来。试看以下两道题：

1）Study the classification below:

Group A: knife, kettle, floor mat, wooden block

Group B: mirror, tin can, fish tank, crystall ball

Which object has been wrongly classified?

(1)knife (2)kettle (3)tin can (4)crystal ball

2)Which of the following materials will you not use to make a pencil holder?

(1)Wood (2)Glass (3)Cotton (4)Rubber