The third and last question are 3 a 2- n force presses down on the marble at the same time as a 1.5n force acts on the right side of the marble 4 a marble rolling downhill suddenly comes to rest at a garden wall

Balanced forces means the forces acting on the object are either equal but in opposite directions or zero.

For the first option, something starting to roll means it has an unbalanced force acting on it.

For the second option, these forces are equal and in opposite directions, so these are balanced forces.

For the third option, the forces are not equal and not in opposite directions, so these are unbalanced forces.

And for the last option, something that changes speed does not have balanced forces.

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.