Seeds placed deep inside the soil do not germinate because they are

Seeds placed deep inside the soil do not germinate because they are unable to get sufficient oxygen.

Germination occurs when seeds transition from dormant to growing living plants. Seeds contain small plants' embryos and all the nutrients a growing plant needs to initiate a growth cycle. Water is one of the most important factors in seed germination as its required for cell respiration, which is a metabolic process. It swells and breaks the seed coat for easy oxygen absorption. Oxygen is also essential for cell respiration, so oxygen must be present for seeds to develop underground. Therefore, it is important not to plant the seeds too deeply. If there is not enough oxygen underground, the seeds cannot metabolise to generate enough energy required to initiate the germination process. When the seedlings grow, they will pop out of the ground. After this stage, germination is complete, and the seedlings can start photosynthesis for energy. 
Hence the correct answer is option A.