You have 50 edge devices in your IoT ecosystem and each of them must run several modules depending on the leaf devices connected to them. The leaf devices change from time to time so do the set of modules to be deployed to a given edge. In order to automate your work and to minimize the deployments needed, you decide to use layered deployment. 
Which of the following modules cannot be part of a layered deployment?

Answer options:

A.edgeAgent module
B.modbusTcpModule
C.streamAnalyticsJob module
D.avroWriter module

Correct Answer: A
Option A is CORRECT because layered deployments are useful in scenarios where the same modules must be used in different combinations in several deployments. Any modules can be deployed by the layered method except for the system runtime modules, the edgeAgent and edgeHub. Target devices of the layered deployment must have the runtime modules deployed beforehand.
Option B is incorrect because any type of custom modules (e.g. modbusTcpModule for communicating with industrial devices) can be deployed by layered deployment.
Option C is incorrect because any type of custom modules (e.g. streamAnalytics jobs for performing data pre-processing locally) can be deployed by layered deployment.
Option D is incorrect because any type of custom modules (e.g. avroWriter for writing data files locally) can be deployed by layered deployment.
References: 

https://docs.microsoft.com/en-us/azure/iot-edge/module-deployment-monitoring?view=iotedge-2018-06
https://docs.microsoft.com/en-us/azure/iot-edge/module-deployment-monitoring?view=iotedge-2018-06#layered-deployment