Answer: C. conservation of number.
Explanation: Conservation of number is a concept which simply shows that the quantity or number of an object doesn't change due to physical repositioning or rearrangement.
For example, we have 26 alphabets in English Language, normally arranged A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z.
If I should rearrange this Letters such that it doesn't follow the alphabetical order, the number of alphabets (26) will still remain the same. This is a good illustration of conservation of numbers.