第一个句子,如果划线部分是he is ,则
Who is running in the playgound?
如果划线部分是running,
What is he doing in the playgound?
如果划线部分是in the playgound,
Where is he running now?
第二个句子,如果划线部分是he,
Who can ski?
如果划线部分是ski,
What can he do?