世界上最早的纸币出现于我国的（    ）

根据中文提示写出单词或词组，使句意完整、正确。 
You should ____（注意）to your handwriting.
Robots can make people____ （懒惰的）.
Let's work together to ____（保护）our would.
You have a toothache. You should go to see a ____（牙科医生）.
My mother likes ____（种植）flowers in the garden.

如图，正六边形ABCDEF内接于⊙O．若直线PA与⊙O相切于点A，则∠PAB=____ ．

人类对地球形状的认识，经历了漫长的探索过程．下列不能说明地球形状为球体的是（    ）