This illustrates <span>absolute threshold. The correct option among all the options that are given in the question is the second option or option "B".
</span><span>A spot in the middle of the retina that only contains cones is called the fovea. The correct option among all the options that are given in the question is the third option or option "C".</span>
The statement that describes the difference between the 2 isotopes of nitrogen would be the last set.
Nitrogen-14 has 7 electrons, 7 protons, and 7 neutrons
Nitrogen-15 has 7 electrons, 7 protons, and 8 neutrons.
The group in which a star is classified according to its spectrum, especially using the Harvard classification.