Answer:
Make sure everyone meets criteria.
Not taking supplements( As some may contain Vit D)
No tanning beds
make sure no one has a hypoactive response to vitamin d through whatever way. Injection, capsule, spray.
Check for genetic conditions or cancers like melanoma which indirectly affect vitamin d levels
Explanation:
These are some of the main things to look out for
This is not a biology question this is a math question
The combined mass of rock 1 and 2 = 19.28 + 25.3
= 44.58
Difference between rock 3 and combined rocks
= 46.3 - 44.58
= 1.72 grams
therefore, the third rock was 1.72 grams greater than the combined mass of the other two rocks.