HOW many  boys are there in the toilet?
回答There is  one 还是 There are  one

There is a  tree and  a flower in the garden.还是There are a  tree and  a flower in the garden.

第一个:用is  因为只有一个!
第二个:用is  因为be动词的就近原则,靠近单数用is,靠近复数用are

Thank you