Look at those flowers,They need 选哪个啊

题目

Look at those flowers,They need 选哪个啊
to be watering
watered
waters
watering
选哪个啊 说下理由谢谢

答案

Look at those flowers,They need （watering）.
瞧这些花.它们需要被浇水了.
sth need doing,某物需要被……,这个词组含有被动的意思.