The main pieces of evidence that an exothermic reaction has occurred is an increase in temperature due to the release of energy, a release of energy in the form of light, or a release of gas.
Answer:
(C) Oxygen because it has the strongest attractive force and the largest
electronegativity
Explanation:
Oxygen will be most reactive
configuration = 
As oxygen need only two electrons to complete its octet.
Oxygen will have stronger force than nitrogen as it will tend to pull electrons more to complete its octet. Also along the period electronegativity increases so oxygen has higher electronegativity than nitrogen
Ruler is the answer of this question
Answer:
B. control rods and moderators