link a port

A user is attempting to link a port on the left to another port in a different transformation on the right. The Designer will not establish the connector link (blue arrow). What are the possible reasons for this?

Choose Answer

(A)
Link columns mode not set, or left port not an output port
(B)
Link columns mode not set, or left port not an output port, or data type mismatch
(C)
Link columns mode not set, or left port not an input port, or right port not an output port, or data type mismatch
(D)
Link columns mode not set, or left port not an output port, or right port not an input port, or data type mismatch