The concept of knowing who we are and how we understand ourselves, as well as how others define us, is called a. gender b. ethnicity c. nationality d. identity

Identity.

Gender is exclusive to the physical body; ethnicity is exclusive to where you are from genetically; nationality is exclusive to what country you are from. Identity is knowing who you are as a person and what others know you as, beyond race, gender and citizenship. :)

So  if  the sum of the enthalpies of the reactants is greater than the products, the  reaction  will be  exothermic.  if  the products side has a larger enthalpy, the  reaction  is  endothermic. you may wonder why  endothermic reactions, which soak up energy or enthalpy from the environment, even happen