Answer:
i would say that D. The button has fallen on the floor. is the most logical explanation
Step-by-step explanation:
it cant be A bcs how shiny the button is doesn't have anything to do with it becoming detached.
it cant be B bcs if it were securely fastened it wouldn't fall off.
it cant be C bcs you can still wear the shirt. and u could sew it back on or whatever.