I'm really sure that the answer is B
Sound waves<span> coming from farther above, where it is warmer, will experience a refraction. The change in speed from the warmer </span>air<span> to the cooler </span>air<span> causes a bending effect, as the </span>sound travels<span> downward.</span>
Okay we are gonna use A iPhone to a old telephone so the telephone can only receive calls and call other people that it but say with the iPhone you can call the person and receive calls you can text you can video chat you can get emails you can have apps to entertain you you can have pictures and music you can have a ringtone and and text tones
The correct answer would be Fluoride was not used to help protect teeth then
Cavity is not a genetic disease and thus there is no relevance of gene transfer in this case. Thus option A, B and D gets ruled out.
However, flouride in a limited amount is very useful for removing the cavities. Flouride in the foood and water enters the blood stream and make the teeth strong from inside. While the Flouride in Saliva make the teeths stronger and cavity free from outside. It reduces reminization that causes the loss of minerals.
Thus lack of flouride makes the teeth more cavity prone.
