a student observes that the grass in his yard begins to die during the hot summer which of the folowing is a valid hypothesis for why the grasses seems to be dying

No 1 very mooch

It is called the medulla oblongata or people usually call it medulla. it is the lower half of the brain stem continuous with the spinal cord. 

A  reaction  in which  energy  is  released  to the surroundings is called an exothermic  reaction. in this type of  reaction  the enthalpy, or stored  chemical energy, is lower for the products than the reactants. when ammonium nitrate is dissolved in water,  energyis  absorbed  and the water cools.