If a person is in front of a smooth surface from which a sound is reflected, the person would hear a sound that
a. seems to come from behind the surface.
b. has a higher intensity than the sound produced by the source.
c. has a higher pitch than the sound produced by the source.
d. seems to lack overtones.

typically, most spiders possess eight eyes. however, others have as many as 12, and some don't have any. these eyes are for detecting light from dark, deciphering shapes and for gathering their prey.

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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