Changing environments or major historical events.
I think the correct answer is the first option. The key features of chordates would be notochord, dorsal tubular nerve cord, pharyngeal pouches, and a tail. These features appears in some period of their lives. They are deutorostomes where the anus would be formed first before the mouth.
Answer:
c
Explanation:
Viruses are like hijackers. They invade living, normal cells and use those cells to multiply and produce other viruses like themselves. This can kill, damage, or change the cells and make you sick. Different viruses attack certain cells in your body such as your liver, respiratory system, or blood.
