Which of the following reactions taking place in the blast furnace during extraction of iron is endothermic?

In this portion, limestone gets decomposed and the resultant lime (CaO) acts as flux, combines with silica (present as impurity - gangue) to form calcium silicate (fusible slag). The reaction is endothermic as heat is required to break chemical bonds in the compound undergoing decomposition.CaCO3​→CaO+CO2​CaO+SiO2​→CaSiO3​