Which of the following describes a handle (as applicable to LR-parsing) appropriately?

It is the position in a sentential form where the next shift or reduce operation will occur

It is non-terminal whose production will be used for reduction in the next step

It is a production that may be used for reduction in a future step along with a position in the sentential form where the next shift or reduce operation will occur

It is the production p that will be used for reduction in the next step along with a position in the sentential form where the right hand side of the production may be found