In a concentrated solution there is
a- no solvent
b- a large amount of solute
c- a small amount of solute
d- no solute

In a concentrated solution there is a large amount of solute. The answer is letter B. It may also be called a supersaturated solution wherein there is a greater amount of solute than the solvent. Having lower solute than the solvent is  called a unsaturated solution.

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.