B -- > 'The debug levels assigned to your trace flags control the type and amount of information that is logged for different events'
C --> System.debug(...) this method placed in different code locals allow the control of information logged
D ---> 'the level is cumulative, that is, if you select FINE, the log also includes «logged at DEBUG, INFO, WARM and ERROR levels.

B -- > 'The debug levels assigned to your trace flags control the type and amount of information that is logged for different events'
C --> System.debug(...) this method placed in different code locals allow the control of information logged
D ---> 'the level is cumulative, that is, if you select FINE, the log also includes «logged at DEBUG, INFO, WARM and ERROR levels.

B,C,D

B,C,D

A, B and D