A child may be more willing to ask the question, but because crossdressers are not seen and recognized all that often, people of any age can call it into question.
A number of years ago I was performing in a CD show. After a rehearsal, we went to dinner at a restaurant. They were quite busy, so there was a line. We went early and had a table reserved. The bill was paid and we were leaving on our own to go back to get ready for the show.
I left while there were still a number of people at the table. As I was walking out, I overheard an elderly woman say to her friend, “You see that table of women over there? I don’t think they’re women, I think they’re men.” It wasn’t said maliciously or with disdain, but with curiosity. I didn’t say anything, nor did I hang around to hear a reply.
An adult will usually not ask directly, but will still take notice.
The girl was asking an honest question, and giving her an honest answer would help teach the next generation that we are not freaks but are just normal people who do things a little different. We create an ally for the next generation