Selectively represent trials in a loop and merge block

Hello! I have a question about loop and merge.
I have one loop and merge block (block1), with 100 items that participants need to study. For each item, participants need to answer for a question with two options (A/B, represents two study strategies). Then based on the choice A or B, I need to represent block 1 again, but in different way. For those items with A choice, I need to present Field 1 in the loop and merge. For those items with B choice, I need to present Field 2 in the loop and merge. How can I fulfill this?
I don't want to set every item with a display logic. Is there any simple way to solve this problem?
Thank you very much!