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
After discussing the matter with the bank manager, Peter ______received his loan.
A．instantly
B．instinctively
C．casually
D．unexpectedly
单项选择题
Slowly, without trying to defend himself, the buffalo sank to his knees and, with one lion______ his throat and another his muzzle, died of suffocation.
A．hold
B．held
C．holding
D．being held
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