Questions with can

Use can every time regardless the subject.

Auxiliary	Subject	Verb	Complement	Short answer
Can	you	speak	English?	Yes,	I	can.
Can	you	climb	a tree?	No, No,	I I	can't. cannot.
Can	he	play	rugby?	Yes,	he	can.
Can	Mandy	read	poems?	Yes,	she	can.
Can	they	sing	nice songs?	No, No,	they they	can't. cannot.

In WH-questions (questions with question words) can goes after the question word.

Question word	Auxiliary	Subject	Verb	Complement	Answer
What	can	they	ride?		They can ride skateboards.
Where	can	Frank	play	the trumpet?	Frank can play the trumpet in his room.
When	can	she	see	her friends?	She can see her friends after school.

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