Answer:
oxygen
Explanation:
its the only element needed
Answer:
The early Earth was very different from our Earth today.
Explanation:
Earth's first atmosphere had lots of water vapor but had almost no oxygen. Later, frequent volcanic eruptions put several different gases into the air (Figure 12.13). These gases created a new type of atmosphere for Earth.
Meory T cells are defined as a subset of infection including cancer-fighting T cells
