Using real-time data ingested from hundreds of sensors connected to your IoT hub, you need to extract, aggregate and send some key data to PowerBI dashboards for real-time visualization where, besides the real-time values, you also need to show trends from the past 14 days. You need to use Stream Analytics to feed data to Power BI. You notice that trends only cover the past 7 days. 
Which of the following is the recommended, cost-effective solution for this use case?

Answer options:

A.Use separate Stream Analytics jobs for real-time dashboard and for the trend display
B.Set the IoT Hub retention time to 14 days
C.Use Stream Analytics for real-time dashboards and feed trend charts from a Storage container
D.Use a dedicated IoT Hub

Correct Answer: C
Option A is incorrect because both jobs will use the streams of the same IoT Hub with the same retention time, which is probably set to 7 days (which is the upper limit), i.e. data beyond 7 days still not will be available.
Option B is incorrect because the maximum retention time for IoT hubs is 7 days, with the default of 1 day. For standard hubs, higher values cannot be set.
Option C is CORRECT because Stream Analytics is great for feeding real-time data to Power BI, while data can be sent to Azure Storage for historical analysis, e.g. for trend analysis.
Option D is incorrect because dedicated IoT hubs provide a retention time of 90 days. Although the option is valid in itself, it is not the recommended solution to use for historical data.
References: 

https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-devguide-messages-read-builtin
https://docs.microsoft.com/en-us/azure/stream-analytics/stream-analytics-define-inputs?view=iotedge-2018-06