You serve as a KMS Key Administrator for your company department.You’ve created a new KMS CMK with imported key material. You’re importing the key material into the KMS CMK. The import operation is failing. What are the possible causes of this problem (Select TWO)?

Answer options:

A.You did not update the key material Origin value to INTERNAL.
B.Your key material is not a 256-bit symmetric key.
C.You did not update the KMS CMK state to “Pending Import”.
D.You waited longer than 24 hours and the import token has expired.

Answer: B and D
Option A is incorrect because for importing key material, you need to firstly create a symmetric CMK whose origin is 
EXTERNAL
.
Option B is CORRECT because the key material for customer-managed CMK must be a 256-bit symmetric key.
Option C is incorrect because a user cannot update the KMS CMK state.
Option D is CORRECT because the import token has a 24-hour expiration time.
Reference:
https://docs.aws.amazon.com/kms/latest/developerguide/importing-keys.html
https://docs.aws.amazon.com/kms/latest/developerguide/importing-keys-get-public-key-and-token.html