Answer:
B. savant syndrome.
Step-by-step explanation:
Savant syndrome:
Savant syndrome is also known as idiot savant or autistic savant. In this condition the person has less intelligence you can say below the average but they have some mental abilities which are more than average. Just like Sandra, she is going through below normal average but she can tell you the exact week day of September 13th, 1957. This shows her above average capacity.
So, according to above evidences, Sandra has savant syndrome.