Multiple choice

The first form of living organism on earth was the _______.

  1. fish

  2. bacteria

  3. tortoise

  4. blue-green algae

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The earliest life forms on Earth were simple, single-celled organisms like blue-green algae (cyanobacteria), which appeared around 3.5 billion years ago. These photosynthetic bacteria were responsible for producing oxygen in Earth's atmosphere.