One disadvantage of cloning is

a-scientists can study why nerve cells don't multiply

b-allows the continuation of species facing extinction

c-scientists can study how organisms grow and reproduce

d-new organisms are often sickly and do not live long lives

Disadvantage of cloning is new organisms are often sick and don't live long.

Explanation:

Cloning is considered to be one of the biggest scientific achievements of mankind to clone any organism or species is just like replacing it with a new one but at the cost. As this species develops disease quite easily and has a shorter life span as the scientist has discovered that the genetic constituent in the genome of the species changes as a reaction to the reproductive system a similar type of system works in binary format and creates two identical or twin species. This evolutionary process creates a distinction among the fittest and finest species which ultimately results in another end to slow down the functioning of basic body parts or premature death.

Increased profits reduced health risks