3 is the answer because they play a key role in the nitrogen cycle.
I'm not positive but i believe it would be a ruler with millimeters and centimeters
It allows it to hide under but still be able to see above it to catch flies
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
