Answer: All of them technically
Explanation: Vigorous definition is characterized by or involving physical strength, effort, or energy.
First is the brain, spinal cord, and heart begin to develop. Then A blood vessel forms which will later develop into the heart and circulatory system.
It's the Lowest concentration of a chemical which prevents visible growth of a bacterium.
That's your answer.
Less stress when you more positive you dont get stressed so easily
