A cold front forms when A.
cold air rises and creates a vacuum.

B.
cold air moves under warm air and pushes the warm air upwards.

C.
warm air collides with cold air, but neither has enough energy to move above or below the other.

D.
warm air moves in below existing cold air and pushes the cold air upwards.

E.

h

h

h

h

h

h tasty

Explanation:

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.