Ageneral term for a chemical which accelerates a reaction without becoming chemically involved is called a
energizer
activator
accelerator
catalyst

D. Catalyst

Explanation:

A catalyst is a substance that speeds up a chemical reaction, but it is not consumed by the reaction. Hence a catalyst can be recovered chemically unchanged at the end of the reaction .

A catalyst lowers the activation energy and hence a large number of reactant particles collide and undergoes reaction. The particles have enough energy since the activation energy which is the minimum energy required for a reaction to occur becomes less.

the positions which points up in upward carbon and down in downward carbon are axial

and vice versa holds true for equatorial positions

so the correct answer with labelled diagram will be