Which Two Public Methods Must Be Implemented in a Functional

Multiple Choice

Which two public methods must be implemented in a functional custom shipping method directly extending Mage_Shipping_Model_Carrier_Abstract and also implementing Mage_Shipping_Model_Carrier_Interface? (Choose two)

A) collectRates ( )
B) getAllowedMethods ( )
C) isTrackingAvailable ( )
D) isFixed ( )
E) getConfigData ( )
F) checkAvailablesnipCountries ( )