Answer: 2. cannot be an element.
Explanation:
Element is a pure substance which is composed of atoms of similar elements.It can not be decomposed into simpler constituents using chemical reactions.Example: Copper 
Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.It can be decomposed into simpler constituents using chemical reactions. Example: methane 

Thus as it can be decomposed into its constituent elements, it is a compound.
Mixture is a substance which has two or more components which do not combine chemically and do not have any fixed ratio in which they are present.
Thus methane cannot be an element.
I believe the correct answer from the choices listed above is option A. <span>A forward reaction in which adding heat decreases product formation is exothermic, while a forward reaction in which adding heat increases product formation is endothermic. Exothermic would mean that heat is being released by the process while the opposite is called endothermic in which it absorbs heat.</span>
I disagree, because a physical change changes the form, and a chemical change is a process where one or more substances are altered into new substances.