What does a positive AH tell about a reaction? A. The reaction is exothermic.
B. The reaction has heat as a product.
C. The reaction is endothermic.
D. The reaction has no activation energy.

Explanation:

There are two main types of reactions classified according to heat: exothermic and endothermic.

The ΔH is the change in enthalpy. It is the difference between the heat of the products and the reactants (ΔH = heat of products - heat of reactants). It helps us describe a system's change in heat and classify reactions as exothermic or endothermic.

In this problem, the change in enthalpy is positive. The change in enthalpy doesn't refer to heat as a product or activation energy. Therefore, the reaction must be endothermic.

the mantle

explanation:

earth is divided into three layers: the crust or the outermost layer on which we live; the underlying, middle layer - the mantle - and the core (the innermost layer of earth).