What is the size limits for attachments while using On-Demand email to case?

Answer options:

A.25 MB
B.50 MB
C.No limit
D.35 MB

Correct Answer: A 
When using on-demand email to case, the size limits for attachments is 25 MB. 
Reference:

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