Reading your mind!

 I was reading a journal. On the last pages there were a maths question page called"Miss Mind Reader" by Joy Cowley. We were a bit curious so my teacher decide that we'll reading it. And any number we choose it equals D. Just read this and you'll know. And we thought that this isn't Mind Reading, that's cheating! So my teacher told me to figure out is this true or not. And, just read and you'll know that. And there's a trick why it is always D. The trick is under, if you want to have fun, skip it. But first you have to do this, figure out the trick. And then look at the answers that is on the side my work. I did all my best. I hope you had fun with it.

The trick is: Any number that multiplies 9 from 1 to 10  add up the digits equals 9.