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Let's study ________ next.
[
A
B
C
D
Hobo doesn’t know ____________ .
A．when to do
B．what to do
C．how to do
D．where to do
They haven't decided ________ next yet．
A．how to do
C．what to do it
D．where to go to
Hobo doesn't know ________．
I don't know ________．
C．where to do
D．why to do