Answer:
D. the red disk about twice as often as the green disk
Step-by-step explanation:
I predict that the bird will peck that the red disk about twice as often as the green disk.
This is because it will take the VI 20" schedule twice of what it will take VI 10" schedule to deliver food to the pigeon.
Also, the pigeon will pick up the behavior that the VI 10" schedule delivers faster when it pecks on the red disk.