Question

By comparing reaction times across different tasks, donders was able to conclude how long the mind needs to perform a certain cognitive task. donders interpreted the difference in reaction time between the simple and choice conditions of his experiment as indicating how long it took to

Answer 1

I believe the answer is: make a decision about the stimulus.
It's written in this part of the research:
. . .difference in reaction time between the simple and choice conditions of his . .
Simple conditions resulted in fast reaction time, which also make it faster for individuals to make a decision about the stimulus. The opposite would happen if the conditions are more complicated.