What it eats, what weather it's build for and DNA
Answer
Just think critically about why (if you were an egg laying species), having a fetus/baby develop inside of you would be advantageous.
For one, eggs are much less protected from outside factors such as predators, temperature, etc than live birthed creatures. Live birth provides protection inside the mothers body from things such as heat, cold, moisture, predatory animals, etc. An egg laying animal must keep its eggs at a perfect temperature and check to make sure no other animal has eaten them.
Any photos below 7 is known as acidic, the lower the pH the more acidic the solution I believe.
