Answer:
Long necks were a random genetic change and resulted in the gradual increase of organisms with long necks.
Sink holes and crevasses might be a result of this <span />
The reason why nost scientists thought that the first true cells formed on Earth were anaerobic is being shown in the second option :B. because there was no oxygen on early Earth. Paying attention to this fact scientists discovered that first cells were prokaryotes and greatest part of them created oxygen as a toxic by-product of their own metabolism which make them understand how the planet was provided with oxygen and made a conclusion that first cells were anaerobic.
