A. True
They are formed behind an obstacle when the wind blows the sand up to it.
Answer:
The first one would describe it best
Explanation:
The second option sounds like a single displacement reaction
The third is a decomposition reaction
ANd the first is a combination reaction
Answer:20
Explanation:because you have to devide
Molar mass is 28+32 = 60
So take 3.4 x 10^-7/60 and get about 5.7 x 10^-9