Use 8 Loop & Merge blocks, one for each category, where the entities are Loop & Merge fields (1 row per entity)
You could randomize the entities and 'present only' 25 loops in the loop & merge setup. Alternatively, to ensure a randomly even distribution, you could create a multiple choice question prior to the loop & merge block with all the entities as choices and advanced randomization to display 25 'evenly presented.' Then hide the MC question with JS and base the loop & merge off the displayed choices in the MC question.

I applied the loop and merge approach.
But there is another issue that came out: an issue with the survey raised by one of the testers. At a certain point when the tester was working on the survey, the browser crashed.
In order to continue to fill in the survey from the moment she stopped - I generated a link for her using the "retake response" function. Once she opened the link - we see that the questions that were implemented with the "loop and merge" function aren't filled. (even if she filled them in the previous session and I could see the filled answers by checking them in the "data and analysis" session). Is there a way, in this case, to keep working on the survey with the recovered answers that were recorded in the previous session?

https://www.qualtrics.com/community/discussion/comment/31028#Comment_31028I don't understand why you did a retake response if she didn't finish the survey. That means you would have had to close the partial first. If you have Save & Continue turned on, she could pick up where she left off using the original link.

https://www.qualtrics.com/community/discussion/comment/31030#Comment_31030Thanks for the prompt response! Yes, save and continue is ON in that survey, but somehow it displays in the "recorded" section, not "in progress" as it supposes to be. (not sure why..)

https://www.qualtrics.com/community/discussion/comment/31033#Comment_31033I'm not sure why either unless the tester went back and finished the survey using the original link after the browser crashed.

https://www.qualtrics.com/community/discussion/comment/31034#Comment_31034I didn't ask that but I think if her survey is displayed in Qualtrics as "completed", once she will use the original link - she will get the blank survey, isn't it?

It depends on survey settings, but most likely she would get a message like, "You've already completed this survey" if she had already completed and used the original link. However, if her browser crashed the first time, when she came back she would have picked up where she left off. Her survey would have displayed as "completed" after she came back and completed after the crash.

I got more details that are hopefully useful to solve this:
She started to fill the survey for the first time and then wanted to reset it. However, as you also explained using the original link she would have picked up where she left off. She figured out how to start filling the survey from scratch by using another browser in incognito mode. Then she explained, "I got to the end and then went back to uTest and clicked on the survey again. Normally after I finish a survey it will go right to the end and say that I have already completed the survey. It didn’t do it this time :(( It starts all over from the beginning."
After that, I found her survey in the status "completed" and to let her edit some of the responses as I said I generated the link using the "retake response" function. But once she used it - she couldn't find her previous responses filled for the questions that used the "loop and merge" function.