CBSE Class 10 Answered

Firstly, i would like to provide some basic concepts before giving the answer of this question.

The exothermic/endothermic nature of a reaction depends on the relative strength of the bonds that are being broken and formed (making and breaking bonds is the essence of a chemical reaction). If the bonds formed in the products are stronger than those in the reactants, the result is release of some energy(exothermic). A stronger bond means that you have to put in more energy in order to break it (endothermic), so when it forms it must release that additional energy.  

a)Dilution of sulphuric acid is exothermic

H₂SO₄ + H₂O → H₃O⁺ + HSO₄⁻

For your Dilution of sulphuric acid, the bonds between water molecules and the bonds between the ions in those compounds you added will have a certain amount of energy. When they dissolve, those bonds break, and new bonds between the water molecules and the ions will be formed. If the new bonds are stronger, the dissolution will be exothermic. 

b) Dilution of sodium hydroxide is also a exothermic reaction and the same concept as above will also apply to this reaction.

c) Decomposition of ferrous sulphate is endothermic reaction 

2 FeSO₄ → Fe₂O₃ + SO₂ + SO₃

as energy is being added to the reactant side.