Is this your backpack?变复数要怎么变啊!

is this your skirt this is your Maybe this is your Is this your uncle? this is your aunt. is this your business Is this your schoolbag? Is this your (空格) Is this your schoolbag? this is your pencil Is this your cake. This is your explanation? Is this your-----photo This is your destiny Is this?your friend is This is your?is this your?求区别! Is this girl your friend?Is this your girl friend? is this your baby?复数