Stephanie has been doing research on how petroleum is formed. she says that oxygen must be present while the tiny plants and animals are being compressed. is stephanie correct?

No, Stephanie is incorrect. Formation of petroleum cannot take place under the presence of oxygen.

Explanation:

Since, the petroleum is fossil product. Fossil fuel are formed under high pressure and temperature with absence of oxygen for longer period. so the way she is performing is completely incorrect. With the presence of oxygen in no way petroleum will be formed. The temperature and pressure should be in different combination for the formation of the petroleum. Along with the layers of sediments to maintain the pressure is required.