the postcard is (mine) 对括号内提问 __ __ the postcard?

the postcard is (mine) 对括号内提问 __ __ the postcard?
the boy on the black bike is (my) cousin 对括号提问 __ __ is the boy on the black bike?
the books on the shelf are (one of my friends'） 对括号提问 __ __ the books on the shelf?