Concept:
Compound words starting with the prefix "back-" have distinct meanings. Choosing the correct word requires matching the prompt's description with the appropriate term.
Step 1: Define each term starting with "back-".
* backlog (noun): An accumulation of uncompleted work or matters that need to be dealt with.
* backlash (noun): A strong, sudden, and adverse reaction or counter-response among a large group of people, especially to a political or social development.
* backache (noun): Prolonged pain in the back.
* backhanded (adjective): Feigned, ambiguous, or sarcastic (e.g., a backhanded compliment).
Step 2: Connect with the definition.
* The phrase "sudden violent reaction" describes a forceful response or pushback against an action, which matches the definition of a backlash.