— Are there two cats in the tree?
— Yes, there are. (No, there aren't.)
C、特殊疑问句及其回答 
a. 提问句子的主语（包括主语前的修饰语）时，句型一律用“what is+地点介词短语？”（无论主语是单数还是复数都用is）。
例：There are some birds in the tree. →  What's in the tree? 
b. 就there be后面的地点状语进行提问时，句型用“where is/ are+主语？” 
例：There is a car in the street. → Where is the car?
c. 提问可数名词（主语）前的数量时，用how many，句型结构为“how many+ 复数名词+are there+其它）”（主语无论是单数还是复数，be通常要用are）。 
例：There are three books on the desk. → How many books are there on the desk?