What can explain the formation of a rock layer with no fossils in between rock layers with different types of fossils?

Specific environments favor the presence of life forms, and their preservation to form fossils, than others.

Explanation:

The reason for the formation of a rock layer with no fossils in between rock layers with different types of fossils is that "Specific environments favor the presence of life forms, and their preservation to form fossils, than others."

For example, the environments in which a particular rock layer developed is likely to differ from the environment from which the subsequent rock layer is formed.

Therefore, one environment supports life forms and formation of fossils while the other doesn't. This can also be caused by the major difference in climatic occurrence or presence.

the first one is d and the second a