Which subatomic particle is the hardest to observe and why

Chen drew a diagram to compare the ways in which different organisms obtain nitrogen. which label belongs to the area marked z?

There is one girl i like and i don't know how to tell her that, i have a feeling she knows but if she doesn't i don't want to make a fool out of myself how is one way to boost my confidence on asking her out

Which is an example of the practical pursuit of alchemy? a. forming perfect substances. b. transforming base metals. c. developing metalworking techniques. d. linking spiritual characteristics with material substances.