Active charcoal is a good catalyst because:
A.it is made of carbon atoms
B.it is very reactive
C.it has more adsorption power
D.it has inert nature towards reagent

Hint: In chemistry, a catalyst is any substance that increases the rate of a reaction without being consumed. Enzymes are naturally occurring catalysts that catalyze many important biochemical reactions. The majority of solid catalysts are metals or their oxides, sulfides, and halides, as well as the semi metallic elements boron, aluminum, and silicon.

Complete answer:
Charcoal is a lightweight black carbon residue made by strongly heating wood (or other animal and plant materials) in a low-oxygen environment to remove all water and volatile constituents. The heat is supplied in the traditional version of this pyrolysis process, known as charcoal burning, by burning a portion of the starting material itself with a limited supply of oxygen. It is also possible to heat in a closed retort.
This process occurs unintentionally when burning wood, such as in a fireplace or woodstove. The visible flame in these is caused by the combustion of the volatile gases expelled by the wood as it burns to become charcoal. The soot and smoke produced by wood fires are the results of incomplete combustion of that volatiles. Charcoal burns at a higher temperature than wood, with a barely visible flame, and emits almost nothing except heat.
So, The catalyst is a substance that interacts with the substrate to catalyze the reaction but cannot interact with the reagents. As a result, active charcoal is a good catalyst because it is inert to the reagent.
Thus, the answer is option D: it is inert to the reagent.

Note:
Activated carbon, also known as activated charcoal, is a type of carbon that has been processed to have small, low-volume pores that increase the available surface area for adsorption or chemical reactions. Active is sometimes used instead of activated.