单项选择题

Programmed instruction received its major impetus from the work of behaviorist J. H. Skinner, who after years of research,______ a practical system in 1954.

A．described
B．derived
C．imitated
D．devised
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单项选择题
At first, the ______of color pictures over a long distance seemed impossible, but, with painstaking efforts and at great expense, it became a reality.
A．transaction
B．transmission
C．transformation
D．transition
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