be動詞例句：
The man is a science teacher.
這個男子是一位科學教師。
Mary's new dresses are colourful.
瑪麗的新衣服色彩鮮豔。
I have been there before.
我以前去過那裡。
My mother is in the kitchen now.
我媽媽現在在廚房裡。
這四個都是陳述句，可以變成疑問句，方法簡單，把主語和“be”或助動詞對換位置即可：
Is the man a science teacher?
Are Mary's new dresses colourful?
Have I been there before?
Is mother in the kitchen now?