Which of the following elements will share the most similar reactions when placed in water? a. two elements in the same period. b. two elements with the same number of energy levels. c. two elements in the same group. d. two elements that are both located to the left of the zig-zag line.

If I had to answer, I would go with C.) Two elements in the same group

I would choose C because elements in the same group have the same number of valence electrons. When elements have the same number of valence electrons, they are all willing to give/receive them in the same way. Therefore, if placed in water, they will combine with water the same way. 

Hope this helps!