【1】
One and two (is) three意思是1+2=3
数字都当作单数名词处理,所以用is
注意在数学中and有“加”的意思
【2】
1、This is my book?
Is this my book?
Yes,it is.
No,it isn't.
2、His family name is Tom.
Is his family name tom?
Yes,it is.
No,it isn't.
3、There are in the classroom.
(我觉得There应该是They)
Are they in the classroom?
Yes,they are.
No,they're not.
【3】
yello（黄色,是颜色colour的一种）
对yellow单词提问
His hat is yellow.
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What's the colour of his hat?