In Genetic Engineering, Why Is It Necessary to Clone the Genes

In genetic engineering, why is it necessary to clone the genes you want to transfer?

A) So there are enough copies to work with, as genes are not simply insertable one at a time
B) So you can transform many generations of cells at once
C) Each single clone is a bit different, so it takes a find the required base sequence for the job.
D) So you can give copies to many scientists to increase the odds of someone figuring out how to engineer the plant
E) It's a precautionary measure in case you destroy the gene you need in the process of inserting it.