If a Scientist Wants to Insert a Gene to Transform

If a scientist wants to insert a gene to transform a cell, why is it necessary to attach "stop" and "start" sections to the gene?

A) The cell's DNA must be able to "read" where the gene stops and starts to make it work.
B) This is how the cell will be able to determine where the gene starts and ends so it will know where in the DNA it should go.
C) A gene only works by being translated, so the translating enzymes have to know where to stop and start reading.
D) Because the gene is artificially engineered, a cell doesn't automatically know where it stops and starts.
E) Scientists do this for themselves, so they can see where the gene stops and starts.