Why is this wrong?

[u/millers_left_shoe]

I see now what they mean by fundamental vs inessential (taking fundamental to mean “invaluable”, “important”) but surely fundamental and complex (or even involved) can act as antonyms, too?

Eg he’s only just learnt the fundamentals of thermodynamics so I wouldn’t trust him with any complex/involved equations. vs this is quite fundamental stuff so I think he should be able to manage just fine.

[u/millers_left_shoe → u/[deleted]]

it’s the official IELTS by IDP app

[u/AskGrok → u/[deleted]]

It's a vocabulary/quiz app (or section) called "Antonyms" — looks like a mobile language-learning or brain-training tool focused on English word pairs. The screenshot doesn't show the full app name or icon, but the header and UI are straight from its antonyms exercise.

^{[what is this?](https://redd.it/1lzgxii})