Scientists have created genetically modified organisms (gmos) by isolating and then transferring the jellyfish gene for green fluorescent protein into pigs, bacteria, plants, and mice. the result was bioluminescent organisms! these experiments demonstrate thata. genes can only be transferred to other organisms within the same species
b. genes have no difficulty crossing the species barrier.
c. animal genes from one species will not function if transferred into other animals.
d. jellyfish genes may be transferred into other aquatic ectotherms, but not mammals.

b. genes have no difficulty crossing the species barrier.

Explanation:

DNA is a universal molecule, by now it is known that has the same structure in pigs, birds, an other living things.

When a gene is transfer to other species, the most difficult action is that the living thing that is the receptor, can adopt this new sequence of DNA and reproduce it again as part of the new DNA.

In some examples like in pigs and humans, we are so closely that you can use some DNA  pigs or tissues to replace in humans when is neccesary in a surgery.

this is a good question! i'll do some research and come back when i have the answer!