A company wants to deploy a custom solution available from a vendor onto Azure. Where should the company search to see if the solution is already readily available to be deployed?

Answer options:

A.In Azure Security Center
B.In the Azure Marketplace
C.In Azure Advisor
D.In Azure Monitor

Answer – B 
You can look for already solutions in the Azure Marketplace. 
The Microsoft documentation mentions the following. 

Since this is clearly mentioned in the Microsoft documentation, all other options are incorrect. 
For more information on the Azure Marketplace, please visit the below URL- 

https://docs.microsoft.com/en-us/azure/marketplace/marketplace-faq-publisher-guide