Correct answer is (D. Once created in bone marrow, they circulate for our lifetime)
The speed of the cross country runner is equal to 4 km/min.
<u>Given the following data:</u>
To determine the speed of the cross country runner:
Speed can be defined as the distance covered by an individual per unit time and it can be measured in kilometer per minutes (km/min).
Mathematically, speed is given by the formula;

Substituting the given parameters into the formula, we have;

Speed = 4 km/min.
Read more: brainly.com/question/13102821
Conjugation is when genetic material is transferred from one bacteria to another via direct contact. Neither of these options are completely correct, but the more correct one would be the first.