The correct answer is 3, meaning that statements 1 and 3 are correct.

Statement 1 states that "The Earth’s magnetic field has reversed every few hundred thousand years." This is known to be a fact. Earth`s magnetic field does undergo what`s called geomagnetic reversals, where the North and South Magnetic Poles switch places, approximately every several hundred thousand years.

Statement 2 highlights that "When the Earth was created more than 4000 million years ago, there was 54% oxygen and no carbon dioxide." This isn`t accurate. The Earth`s early atmosphere wasn`t rich in oxygen. On the contrary, it was composed mainly of nitrogen, water vapor, and carbon dioxide. Oxygen started to build up in the atmosphere around 2.5 billion years ago, due to photosynthesis by early life forms.

Statement 3 points out that "When living organisms originated, they modified the early atmosphere of the Earth." This statement is true. As life began to evolve on Earth, organisms helped alter the makeup of the atmosphere, notably through photosynthesis which resulted in increased levels of oxygen.

Therefore, the correct options are 1 and 3.