Studies involving humans or animals are conducted under strict policies and procedures. this solution addresses which limitation?

lack of proper equipment
size of the system
limited amount of time
ethical concerns

D.Ethical concerns

Explanation:

Ethics is a term used in scientific experiment to refer to conducting experiments under the correct rules of conduct necessary when performing a research.It is a moral responsibility of a researcher to protect participants in a research from harm.Some of the ethical issues are: beneficence, respecting privacy, informed consent and respecting anonymity and confidentiality.

Option D, ethical concerns

Explanation:

All scientific studies that involve human or animals become a matter of ethical concern and this is so because there are several moral principles of the society which are at stake.

For example - society believes than even an embryo in the womb of a woman, who has not taken birth has the right to live and thus studies such as "stem cell researches"  involving usage of embryonic cell are ethically condemned.

Genetic studies are also a matter of ethical concerns as society believes that hereditary history is a personal matter and should not be tried and tested openly.

Option D is correct

the answers are as following:

1. c. double helix, nucleosome, coil, supercoil, chromosome

2. b. g2 phase, preparation for mitosis

3. d. interphase consists of the g1, s, and g2 phases

4. c. metaphase

5. a. chromosomes are duplicated before cell division so that each new daughter cell has a complete set