Which of the following must be true for the REF (Return

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Which of the following must be true for the REF (Return From Exception)
1. It must be a TRAP instruction.
2. It must be a privileged instruction.
3. An exception cannot be allowed to occur during execution of an REE instruction.

1. 1 only
2. 2 only
3. 1 and 2
4. 1, 2 and 3

Correct Option: D

When an RFE (Return From Exception) instruction is executed; no exception is allowed to occur during that time and also it must be a trap instruction and also a privileged one.
Thus all the three statements are true as far as RFE is concerned.