Final answer:
The question requires estimating the volume of cereal and the size of Wembley Stadium's pitch to determine the depth of cereal, but without specific data, an accurate answer cannot be provided.
Step-by-step explanation:
The student's question is a hypothetical scenario involving volume calculation and estimation. To answer this question, one would need to estimate the average amount of cereal consumed per person at breakfast in the UK, the population of the UK that eats cereal for breakfast, and the size of Wembley Stadium's pitch. However, without specific data on these variables, it is impossible to calculate the exact depth of cereal. This is an exercise in estimation and mathematical reasoning rather than a problem with a definitive answer. Therefore, without the specific data needed for this calculation, we can't select an accurate answer from the options provided.