Conclusion is that seeing the logo has an effect on the ability of the pilots. Usually in cause and effect questions, if we can show another example that given the cause, the effect exists, then that option is usually a good strengthening point.
Lets look at the argument closely in our language,
An experiment is being performed where pilots need to perform a difficult landing in low visibility conditions.
When a logo is present, (Logo is of a big organisation which gives flight training), a 'greater percentage' of pilots are successful. (we need to keep these key words in check, this is a percentage point increase, say without the logo 30% pilots were successful and with the logo 40% were successful.)
Now cause here is the presence of the logo and the effect here is the increase in confidence in pilots seeing the logo. You can think of it as: say you got a 700 level CR question with a tag (700+ super hard Bold face) and you got it right and you reviewed it really well. If a similar question comes up later in your prep phase with a tag (700+ super hard Bold Face) then you feel that hey I solved it last time I can nail that question this time. This conclusion of the argument is somewhat similar.
Now to strengthen we can do the following:
1) Say something else is causing the higher success rate other than confidence (a weaken scenario), then the correct option would counter that weaken by saying something along the line that nothing else could possibly cause this
2) Or we can show that the cause and effect is present in some other form.
Here we go by the second way. Pre thinking: if we can show some relationship between seeing the logo and effect on confidence then that would be a good choice.
A) This option says that regardless of the logo something else is explaining the higher success rate. this weakens. A is out
B) This option doesn't give us a effect, it just says that another experiment was done. We don't know what was the outcome. B is out.
C) Again nothing about the logo. This doesn't really help us. Maybe instruments are useful but we want to support that logo had some effect. So C is out.
D) This option gives the cause and effect in a different way. Thinking of it in our 700 level question analogy: Suppose you got a 700+ hard CR question (tagged as 700 + super hard Bold Face) during your prep and you had no clue about the question. You just skipped it. And then during a review session you see another question along similar lines with the tag : (700+ super hard Bold Face). Chances are you will be low on confidence on this one. This option says the same thing that pilots who failed, will get reminded that they failed and will have that negative effect on performance. So Hold on to D.
E) Pilots who didn't receive UPA training are not in the scope. The question mentions that the pilots in question completed their UPA training. So E is out
D is the answer.
OG 2018 CR 649 (it was a QOTD as well I think) is a very similar question.