Okay I know I am being picky...but why in the world did you title this "Blue Sky".. What you title your images is what you want the viewer to believe your main subject is. I believe you subject as defined by the challenge description is suppose to be the smallest part of your image. That being said I won't judge you by your title......:-)
Meets challenge description.....................10
Meets definition of minimalism...................10
Technical....................................................9 not sure if it is my screen or the image but there appears to be noise or artifacts in it.
Artistic........................................................5 I don't know why this image is not placed more to the center of the photograph.
Your title is blue sky, though the subject here should be the cloud. You completed the challenge description, however I just can't seem to find the subject stand out at me. It doesnt scream "hey look at me again and again".
Sorry, but this just doesn't do it for me... It seems very "empty". I know that a wisp of cloud can certainly be beautiful, but this one doesn't seem to hold anything special. (Sorry - I hate to be negative, but it looks like you cropped it from a much larger image that was probably quite nice.)