How to tell someone that your photograph is your own?

I'm taking a French class online, and one of the assignments was to turn in a photo of something French and translate it in English. I did that, but my teacher thinks I used a picture from the internet. How do I tell her that it is my own photo without sounding rude online? Here is her message:
"This is a great picture, (my name), and your explanation is wonderful. But we can't use a picture from the Internet for this activity. We would like you to look around your own house or community and find something with French on it. It could be cosmetics, food labels, TV and iPhone manuals, soaps, clothes, anything you can find that has French written on it. Take a picture and send it in, telling us what it is."

Take a picture of the object with yourself in the photo as well.

OR

Write your name on a piece of paper, then take a picture of the object / paper together.

If the picture is yours, there are a number of ways to prove it. If you're using a picture from the internet, not so much.

Most digital image files have what is called EXIF data. It records the date, shutter speed, lens aperture, model and brand of the camera. If you had been using a dSLR, any image comment you placed on the camera would also show up.

Telling any one something factual is NOT rude. You are just stating a fact and standing by it. If you flinch, you are showing your instructor that indeed you did find that image on the Internet.

You can use a special program called OPanda that will read the EXIF data for you and you can then send that data along with your email response to the instructor

Here is what that looks like.

Make = NIKON CORPORATION
Model = NIKON D300
X Resolution = 300
Y Resolution = 300
Resolution Unit = inch
Software = Adobe Photoshop Lightroom 4.4 (Windows)
Date Time = 2013-06-17 00:13:38
Artist = Your Name
Copyright = 2013, Your Name, All rights reserved

My camera also records the GPS location.

The date and time

Mademoiselle (her name), votre message est tres prudent mais, je suis desolée porquois votre paroles sont toulemont erronées, et l'explication est clair comme l'aou: je jamais utilizée quelcome image de l'internet
Sorry miss spelling

I don't know why you would have to prove it in detail, she's not accusing you of plagiarism she just thinks you got it off the net ( she sounds more likes she's informing you that you were supposed to take it yourself and you didn't get the memo lol)

Just say you did take it yourself, make it sound nice "I took the picture down at this lovely little cafe" etc

It is really impossible to physically prove you are the photographer since any of the methods mentioned above can be faked.

I would just respond that you indeed did that the photo as the assignment required and leave it at that.