Answer:
The researcher is most likely studying C. absolute threshold.
Explanation:
Threshold refers a specific intensity which needs to be exceeded in order to <em>obtain a certain reaction</em>. For example, pain threshold.
The absolute threshold refers to the smallest change in a <em>stimulus' intensity</em> in order to be <em>identified by the senses</em>, such as hearing, vision, etc.
In this case, a <em>change in tones requires a low intensity</em>, meaning an almost subtle change can be easily identified by the human sense. It is most likely the researcher is studying your absolute threshold.
I think the correct answer would be 43 seconds. Reaction time is the time that it takes for one to react to a certain stimulus. For a car running at 30 mph, it is said that your reaction is about 43 seconds before you could stop the car.
Observervations............
Guide away from the catholic church/views of supernatural and chance
Checks and balances are counterbalancing influences by which an organization or system is regulated, typically those ensuring that political power is not concentrated in the hands of individuals or groups. The delegates made this apart of the U.S constitution so that 1 branch could not over power the other 2.