Which of the following statements is true?
a. most of the nuclear radiation you are exposed to in the environment is man-made.
b. you are exposed to nuclear radiation every day.
c. naturally occurring nuclear radiation is called background decay.
d. all natural radiation is at a level low enough to be safe.

h let me think

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.