Rust forming on a metal gate and milk going sour what do they have in common

There are 6.022 x 10^23 atoms of hg in 1 mole of hg. the number of atoms in 4.5 moles of hg can be found by multiplying 4.5 by 6.022 x 10^23 a. 2.7 x 10^24 b. 27 x 10^23 c. 2.71 x10^24 d. 27.099 x 10^23

Compare and contrast refraction of light and sound will give brainliest

How many grams of mgbr2 are needed to produce 75g or metal?