Concept:
This idiom uses a simple domestic accident to convey a deeper life lesson: once a resource is wasted or a mistake is made, no amount of sorrow can undo it.
Step 1: Trace the literal and metaphorical meaning.
* Once milk is spilled on the ground, it cannot be recovered. Crying or expressing sorrow over it is useless because the event cannot be undone.
* Metaphorically, it advises people not to waste time being upset over past mistakes, historical losses, or unchangeable events.
Step 2: Filter the options.
* (A) worry about the future: Incorrect, as the idiom targets past events.
* (B) plan for the future: Incorrect, as the idiom focuses on processing past losses.
* (C) Happy about something: Incorrect, as crying implies sadness, not joy.
* (D) upset about something that has already happened: Perfectly matches the definition of dwelling unproductively on past events.