Correct Option: B. $A-2,B-1,C-3,D-4$
$$\begin{array}{c l| c l} \hline \text{A.} & \text{DMA I/O} & 2. & \text{Disk}\\\hline \text{B.} & \text{Cache} & 1. & \text{High-speed RAM} \\\hline \text{C.} & \text{Interrupt I/O} & 3. & \text{Printer}\\\hline \text{D.} & \text{Condition Code Register} & 4. & \text{ALU} \\\hline \end{array}$$
Reason:
- DMA I/O - For high speed, high volume data transfer from disk without affecting the processor(in most cases).
- Cache-A high speed & low memory version of a RAM.
- Interrupt I/O - The printer sends an interrupt signal when it is ready for use.
- Condition Code Register - Part of the ALU, as a special purpose register, to store flag bits.
[Source - Google/Wikipedia]