1. —Is this your pencil?
    —No,it isn't. ______ (That,That's) my pencil.
2. —What's this?
    —______(It's, Its) a red pen.
3. I can see______ (a, an) English girl.
4. —______(What's, What)color is the clock?
    —It's white.
5. —Excuse ______ (I, me),Sally. Is this your book?   
    —No, it isn't.