It would be B. change in color
The conditions that must be met before a specific pathogen is proved to cause a disease include; Pathogen must be present in every case in which the disease is found, pathogen must be isolated and grown outside the body in a pure culture, healthy animals infected with culture must develop the disease and finally the pathogen must be re-isolated and cultured from the newly sick animals and must be identical to the original pathogen.
Answer:
External fertilization usually occurs in aquatic environments where both eggs and sperm are released into the water. After the sperm reaches the egg, fertilization can then take place.External fertilization is most common in amphibians and fish.
Explanation:
Some animals produce offspring through asexual reproduction while other animals produce offspring through sexual reproduction.
Sexual reproduction starts with the combination of a sperm and an egg in a process called fertilization. This can occur either outside the bodies or inside the female.There are two types of fertilization in sexual reproduction. Internal fertilization and external fertilization.External fertilization is a common and widespread in aquatic environments where both eggs and sperm are released into the water. After the sperm reaches the egg, fertilization takes place. Most external fertilization happens during the process of spawning where one or several females release their eggs and the male(s) release sperm in the same area, at the same time. The spawning may be triggered by environmental signals, such as water temperature or the length of daylight. Nearly all fish spawn, as do crustaceans (such as crabs and shrimp), mollusks (such as oysters), squid, and echinoderms (such as sea urchins and sea cucumbers). Frogs, corals, mayflies, and mosquitoes also spawn
