Plants are more readily manipulated by genetic engineering than are animals because
a. plant genes do not contain introns.
b. more vectors are available for transferring recombinant dna into plant cells.
c. a somatic plant cell can often give rise to a complete plant.
d. plant cells have larger nuclei

The correct answer is option c. "a somatic plant cell can often give rise to a complete plant".

Explanation:

One characteristic that makes plants readily manipulated organisms for genetic engineering studies is that a somatic plant cell can often give rise to a complete plant. This process is known as somatic embryogenesis, and is widely used with relative ease in biotechnology laboratories. Somatic embryogenesis helps to quickly test genetic manipulation tests in complete plants allowing to check for the final phenotype easily.

i am going to guess that it is co2.