In classic PC partitioning (MBR), how many primary partitions can exist on a single physical drive?

Introduction / Context:
Understanding legacy Master Boot Record (MBR) partitioning is still useful when maintaining older systems or preparing for certification exams. MBR imposes a specific layout and limits the number of primary partitions available per disk, a constraint that shaped common dual-boot and multi-OS strategies for decades.

Given Data / Assumptions:

• The disk uses MBR (not GPT).
• You are counting only primary partitions as defined by the partition table format.
• Extended and logical partitions are considered separately from primary ones.

Concept / Approach:
MBR reserves a table with four entries for primary partitions. You can use all four as primary partitions, or consume one entry for an extended partition, inside which you may create multiple logical drives. This design is a workaround to the four-entry limit without modifying the original MBR specification.

Step-by-Step Solution:

Verification / Alternative check:
Use 'fdisk -l' on an MBR disk to see at most four entries flagged as primary/extended. On GPT disks, you will observe a different, more flexible scheme (often up to 128 partitions by default), confirming that the four-partition limit is unique to MBR.

Why Other Options Are Wrong:

• 16/2/1: Do not match the MBR specification; these numbers can reflect logical partitions or unrelated limits.
• None of the above: Incorrect because the correct limit is four.

Common Pitfalls:
Confusing logical partitions within the extended area with primary partitions, and assuming GPT rules apply to legacy BIOS/MBR systems.

Final Answer:
4