Which will most likely alter the pH of rain

Presence of acidic oxides and other chemicals in air can change the PH value of the Rain.

Explanation:

Generally, PH value of rain remains 5.0. But when the air composition changes due to sulfur dioxide or nitrogen oxides released from automobiles and coal based power plants, the combination of these with rain water makes rainy water more acidic. This results in change of PH value of Rain.

after receiving a stimus, the sensory receptors send(s) signals to the appropriate area of the body.  

the must be sensory neurons.  

hope its .