The last one is the suns energy
B. The earth correct answer.
Reference table J?
In general though reactions happen when one element wants to replace another element in another molecule/compound. So in this case you are essentially looking for the most reactive metal of the 4 choices. Elements become more reactive as you go down the periodic table, and metals become more reactive as you move left along the period, meaning Alkali metals are the most reactive metals, and Francium is the most reactive metal.
Based on this knowledge we can assume that Potassium is the most reactive of the choices and thus most readily reacts with HCl to produce H2 gas. And if you want prood check out this video!
https://www.youtube.com/watch?v=53T5WZHQ_Ck
Wavelength = (planck’s constant) (speed of light) / Energy
6.2 (Energy) = (6.63 •10^-34) (3•10^8)
1.989•10^-25 / 6.2 =
3.2081 • 10^-26 is the answer
