How Are New Conditioned Responses Created in Higher-Order Conditioning

Multiple Choice

How are new conditioned responses created in higher-order conditioning

A)  They are built on the foundation of innate unconditioned responses. 
B)  They are conditioned by repeatedly pairing them with discriminative stimuli. 
C)  They are facilitated by sensory adaptation. 
D)  They are built on the foundation of previously established conditioned responses.