Gabriella and Michelle are a few meters apart, at one end of a football field. Pierre is at the other end of the field, and he sees both of them mov- ing toward him at 4 m/s. From Michelle's point of view, how is Gabriella moving?

She is not moving.

Explanation:

It is stated that Pierre is observing both of them the same way which means that they are both moving in the same direction at the same speed, 4m/s. According to the relative speed concept, they will observe each other according to the difference in their movement directions and speed. Since they are moving in the same direction and at the same speed, Gabriella will be observed as if not moving from Michellle's point of view.

I hope this answer helps.

is called echinoderms

parasites can detrimentally affect their host, but also must not allow their host to die before they can complete their life cycle. some parasites have complex life cycles with many different hosts, and have had to find ways of persisting in many different environments during the change from one host to another. ectoparasites live outside the body of the host, and can more easily  disperse, but are  more exposed to predators, parasites, parasitoids. endoparasites live inside the body of the host, and are therefore protected from the outside environment. but they can be  attacked by the host's immune system. they have therefore developed  mechanisms for dispersal such as  complex life cycles.