A single cell in a smoker's lung has become cancerous. It doubles its DNA and divides much faster than a normal lung cell. The most likely change that would have caused this condition took place in the:

Nucleus

Explanation:

The nucleus is like the brain which controls all cells inside us, which means it controls the split of the DNA  

answer; a muscle cell, another neuron and a of the above

i think that is new experiments yield untrustworthy data and should be carefully considered, because you don't know what will happen with the experiments.