How many sigma bonds in a single bond

single bond= 1 sigma bond

so basically 1

Explanation:

Usually, all bonds between atoms in most organic compounds contain one sigma bond each. If it is a single bond, it contains only sigma bond. Multiple bonds (double and triple), however, contains sigma and pi bonds. Double bonds have one each, and triple bonds have one sigma bond and two pi bonds

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.

the correct answer would be b) volume versus temperature, because they are also directly proportional.