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

[answerhappygod]

a) Position where next reduce or shift operation will occur
b) The next step has use of Non-terminal for reduction
c) Used for reduction in a coming-up step along with a position in the sentential form where the next shift or reduce operation will occur
d) Used in the next step for reduction along with a position in the sentential form where the right hand side of the production may be found