<span>Ultra violet light is the catalyst that converts 7-dehydrocholesterol to provitamin D3. Ultra violet light can be obtained from the sun. The conversion happens when UVB light hits the skin (where 7-dehydrocholesterol naturally resides), gets absorbed, and us metabolized inside of the body.</span>
1 is c 2 is b 3 is 1 d 4 is a
Normal rain has a pH between 5.0 and 5.5. The typical pH value for acid rain (when checked online) is 4.0.
