把下面句子改为被动句
问题描述：
把下面句子改为被动句
I have learned English for about two years
English______ ________ _________ by me for two years
They have sold out the light green dresses
The light green dresses________ ___________ ________out
You must not piant trees in very dry earth
Trees______ _______ ________ ________in very dry earth
You can dig a hole in the earth
A hole__________ __________ __________ in the earth
答
I have learned English for about two years
English " has been learned" by me for two years
They have sold out the light green dresses
The light green dresses " have been sold " out