Exercise 1: Why Reaping Orphaned Processes Is PID 1's Special Job — Possible Solution
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Explanation:

On Linux, every process (except PID 1 itself) has a parent process,
and when a process finishes, its parent is normally expected to
"collect" its exit status via a system call -- until that happens, the
finished process lingers in the process table as a zombie. This is
normally fine, since a well-behaved parent process cleans up after
its own children promptly. The problem arises when a PARENT process
itself dies before its own children do (or before it collects their
exit status) -- the children become "orphaned," with no parent left
to ever perform that cleanup.

This is where PID 1's special role comes in: per the chapter's own
description, PID 1 automatically adopts any orphaned process,
becoming its new parent, and is specifically responsible for
eventually reaping it once it finishes -- preventing it from
permanently lingering as an unclaimed zombie. No other process on the
system has this automatic adoption responsibility -- an ordinary
process whose own parent dies doesn't get reassigned to some other
random process; it's specifically PID 1, and only PID 1, that the
kernel hands every orphan to. This is a structural guarantee built
into how the kernel itself treats PID 1, not a role any other process
could simply choose to take on.

WHY THIS WORKS AS AN ANSWER
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This explains the underlying mechanism (parent processes normally
collect their children's exit status; orphaned children need someone
else to do this) and why PID 1 specifically is the kernel's own
designated adopter, rather than just restating that PID 1 "reaps
processes" without explaining what that means or why it's unique to
PID 1.