Universal Container’s Sales Ops was trying to import some data into Salesforce that contain multi-select picklist. The import file kept giving import errors. Salesforce Admin found that the mapping is done properly so he was trying to investigate the source of the error. What do you think is the reason for the error?

Answer options:

A.The mapping for the fields is wrong
B.The values for multi-select picklists should be separated by a semicolon in an import file
C.The file contains too many columns
D.The data file shouldn’t be a CSV file

Correct Answer: B 
To have the ability to import multiple values to a multi-select picklist, the values should be separated by a semicolon. 
Other Options are incorrect because the mapping is done correctly, and it doesn’t matter if the file contains many columns. And the data file should be a CSV file. 
Reference: 

https://help.salesforce.com/articleView?id=notes_on_importing_data.htm&type=5