The animation is enchanting and the music is charming (you did not give credit for the music). However the subtitles moved too fast for me to read, so if you can slow them down a bit it will help students. I understand now that this is the reason you did not put any introductory paragraph before the question, but even a short statement will do the work, like: "The following animation demonstrates the Hemoglobin molecule. Please watch and answer the following question." Consider that.
The question itself is in a negative format, which is a bit uncomfortable for the students, but the main difficulty is that most of the information on the distractors is a content knowledge that the student should know in advance and not from the animation or the blossoms video linked, making the question to be of the lower levels of the Bloom’s Taxonomy. It will help if the iron atom would appear on the animation and that the distractors will refer to its role on the molecule.