What response articulates proper IP warming?

A large retail company has selected Marketing Cloud and has asked to be fully migrated from their existing platform in three weeks.

They have communicated the following:

* They currently have 3 million customers.

* They email customers twice a week with no known deliverability issues.

* Their contract includes one Sender Authentication Package (SAP).

What response articulates proper IP warming? Choose 2 answers
A . IP ramp-up takes four to six weeks to be able to fully send to all 3 million customers.
B . IP ramp-up can be accelerated by migrating to pre-warmed IP addresses.
C . IP ramp-up is important to establish a positive sender reputation.
D . IP ramp-up can be bypassed, given their historical lack of deliverability issues.