Myron is almost late for class and he is running quickly to arrive before the professor begins lecturing as he listen to the professor lecture myron notices that his heart started beating rapidly and his respiration rate is quite high myron conclude that he must be interested in the lecture abd professor because he would not be so aroused otherwise the theory would best explain myron's conclusion

Myron's processing or feeling based on instinct can be explained using a

theory of emotion.

The theory of emotion is the Schacter-Singer theory of emotion.

Reasons:

The theory of emotion that best explains Myron's conclusion is the

Schachter-Singer Theory of Emotion (Two-Factor Theory), which states

that the emotions of a person are as a result of two factors, which are the

physiological arousal and cognition.

Based on the theory, the environmental context is used to interpret the

psychological arousal.

The arousal of the body which is presented by the rapid heart beat rate,

and high respiration ration, that may be due to his running to class is

interpreted or given cognitive interpretation by the brain, (labelled) based

on his past experience as being  due to his presence in the class of the

professor.

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There is no theory here.
Myron has offered one hypothesis to explain his observations.
There are other possible hypotheses.
They include:

-- An infected mosquito might have bitten him while he slept,
and the results of the infection might be starting to show up.

-- He might have eaten something for dinner last night
that was slightly spoiled.

-- He might have imbibed too much beer for his own good
at the fraternity party last night.

-- There may be too much Carbon Dioxide in the classroom air.

-- His body may be reacting to the physical stress of running to class.

So far, Myron only has a hypothesis.
He's in no position to come to any "conclusion" until he tests
his hypothesis, and shows that the same results follow the same
conditions MOST of the time.  His hypothesis may be difficult to 
test, but until he does that, he doesn't have a theory.

My personal opinion is that while his hypothesis may also be correct,
the most likely source of his observation is the recent physical stress 
of running to class.  It's important to understand that I'm in no position
to try and convince anyone of this conclusion.  My opinion is simply
another hypothesis.  It carries no weight until it's tested.

2. they have negligible mass.