It's the one on the left. We're allowed any calculator that's not programmable and cannot store text. The Elektronika can be programmed though it cannot store a program when turned off.
Nevermind the Casio's ability to solve, integrate, derivate, deal with complex numbers and matrices and more
Now, I would certainly never do this, but almost all TIs that were allowed on SATs and other standardized tests had a program function. These programs didn't necessarily have to run, you could just type whatever like a text file.
The proctors knew about this, and made sure everyone would clear their calculators memory before the exams, and go around to everyone's seat and ensure they had a "memory reset" screen.
That's all well and good; except TIs have an "archive" function. This allows a program to be stored through a memory reset, whilst still displaying the same screen.
As far as I'm aware the proctors never caught on to this. I only discovered it because I didn't want to keep losing the actual programs I was writing in class.