You need to start with the factors that favour germination processes such that: water, temperature, light, oxygen, hence, you may conclude that there exists 4 factors that affect seed germination.
Water is needed in seed germination but a surplus amount of water could destroy the process since this surplus is used by hydrolases, which are factors that stop the germination.
Temperature is also a factor that allows seed germmination process to begin. If the temperature is not proper, the process becomes slower or even stops.
Oxygen is also an important factor that help the germination process, hence, hence, the more anaerobic conditions are, the less germination process becomes posssible.