Which steps require SAP system downtime?

You are importing an SAP Support Package Stack with transaction SPAM.

Which steps require SAP system downtime? Note: There are 2 correct answers to this question.
A . Modification adjustment of other objects (SPAU)
B . Import of inactive dictionary objects (DD IMPORT)
C . Activation of dictionary objects (DD ACTIVATION)
D . Modification adjustment of dictionary objects (SPDD)

Answer: A,C