Data:
Arsenic Molar Mass = 74,9216 ≈ 75 u (<span>atomic mass unit)</span>
Solving:
1 mole of arsenic → 75g ------------ 6,02*10²³ molecules
..................................X -------------- 1 molecule
6,02*10²³X = 75

Number one would be Decades
Because you need to know how/ learn to try new things for (new experiments) and creativity will teach you different ways on how to do it.