Hey Haewon!
Sure! No problem =)
An objection is an argument that opponents (people against Triplett's findings) might bring up.
For example...
If I want to start my own business, an objection to that might be that I'm too young or too inexperienced.
So, people who object to Triplett's findings (the results of the experiment) might object in some way.
Following so far? Good =)
So, Triplett designed his experiment in a way that would eliminate WHAT POSSIBLE OBJECTION?....that is what the question is asking. So the answer will be a possible objection that people might have THAT TRIPLETT ALREADY ADDRESSED WITH THE WAY HE DESIGNED HIS EXPERIMENT.
Hope this helps! It was a difficult because it is asking you to consider the possiblity of several things.
Keep Moving Forward!
You got this!