Q1: In which addressing mode the contents of a register specified in the instruction are first decremented, and then these contents are used as the effective address of the operands?

ANS:D - auto decrement

The auto decrement mode is very similar to the register indirect mode. The only exception is that the register is decremented before (or after) we use its value to access memory. When the address that is stored in the register is defining a data table in memory, it is crucial to decrement the register after accessing the table every time. It can be obtained using the decrement instruction.