Multiple response - answers boxes appear at different times

I have a Storyline 360  file with a multiple response quiz question. There are 7 possible answers. All the answers are set to appear on the screen at the same time in the timeline. In the previewer however, 3 of the answer boxes appear, then about a second later the other 4 boxes appear. I need them all to appear on screen at the same time. How do I do that? Many thanks for any help.