Only 1- the experiment can not show a cause and effect relationship if there are more than one factors contributing to the outcome.
It carries signals for the body through nerves (answer 3)
Answer:
Organ systems: human body and circulatory system
organs: heart
tissue: muscle
Explanation:
<span>The role of a restriction enzyme is essentially used to cut a single gene from a larger piece of DNA. It has a very important role to play in experiments investigating cloning, and in the construction of particular DNA molecules.</span>
