You have a requirement if your search criteria in your Cognitive Search uses “dog”, the documents containing “canine” or “puppy” are also searched. For that you define synonym maps. Review the statements given below regarding synonym maps and choose statements that are true. (choose three statements) 

Answer options:

A.A field can use more than one synonym map
B.Basic tier supports upto 20 synonym maps
C.Mapping rules only support Apache Solr format
D.Portal does not support synonym map definitions
E.Free tier supports upto 4000 rules per synonym map

Correct Answers: B, C and D
Option A is incorrect because a field cannot use more than one synonym map. However, you can create multiple synonym maps based on language or lexicon requirements.
Option B is correct because Basic tier supports upto 20 synonym maps. If you have a requirement to use three synonym maps, you can use the free tier.
Option C is correct because mapping rules only support the solr format.
Option D is correct because synonym maps can only be created programmatically. Portal does not support synonym map definitions.
Option E is incorrect because Free tier supports upto 5000 rules per synonym map.
Reference:
To learn more about synonym maps in cognitive search, use the link given below: 

https://docs.microsoft.com/en-us/azure/search/search-synonyms