The answer is 'D'
(A) The reason that certain spicy foods, such as the Habanero pepper, makes some people sweat is because they contain a chemical that stimulates the same nerve endings in the mouth as does a rise in temperature
'foods' is plural- so it should be 'make'
'The reason' with 'because' is redundant.
(B) The reason that certain spicy foods, such as the Habanero pepper, makes some people sweat is that these foods contain a chemical that stimulates the same nerves in the mouth like a rise in temperature
'foods' is plural- so it should be 'make'
(C) Certain spicy foods, such as the Habanero pepper, make some people sweat because they contain a chemical that stimulates the same nerves in the mouth like a rise in temperature does
'chemical stimulates the same nerves in the mouth' is compared to 'stimulation of nerves by a rise in temperature'-Wrong comparison
(D) The reason that certain spicy foods, such as the Habanero pepper, make some people sweat is that these foods contain a chemical that stimulates the same nerves in the mouth and on the tongue as does a rise in temperature
Correct in both meaning as well as usage of grammar
(E) The reason that certain spicy foods, such as the Habanero pepper, make some people sweat is because they contain a chemical that stimulates the same nerves in the mouth as does a rise in temperature
'The reason' with 'because' is redundant.