I'm applying for position as a c.n.a, and I'm being ask the question (why do I feel qualified for the c.n.a position).

Well as YOU are being asked this, only YOU can answer.

I assume you do actually qualify for this position?

You are qualified based on training, degrees or certifications, and experience with good references.
You want the job based on your love of the work, helping those who need care, your enjoyment of people and social interaction.
You will be good for this or any job because you are reliable, prompt, attentive to detail, always want to learn more, and follow orders well.
Add anything else that 'sells' your good qualities and doesn't sound like you copied it from a generic resume!
For instance, you like to sing, and like to sing a little bit to patients.
You bake, and enjoy bringing in cookies.
You have neat handwriting.
Etc.

Thank u, I've been working as an aid for 10 years any time that question comes I can never put the words together. But thanks ;)