Answer:
it should be changing environment
Scientists think that algae first evolved approximately 2.7 billion years ago, and soon after this oxygen began to exist in the atmosphere. Photosynthesis by primitive plants and algae released oxygen, which gradually built up in the atmosphere.
Explanation:
Pues Yo ni te conozco pero gracias mi vida jajaja
Answer:
a map
Explanation:
The sentence says: I use a map to navigate (or to cross)
