**Core Concept**
Lithium potentiates the action of non-depolarizing muscle relaxants by increasing the release of acetylcholine and enhancing its action at the neuromuscular junction. This is due to lithium's ability to inhibit the sodium-potassium ATPase pump, leading to increased intracellular sodium and calcium levels, which in turn enhance acetylcholine release.

**Why the Correct Answer is Right**
The correct answer is based on the principle that lithium should be stopped 24 hours before the administration of non-depolarizing muscle relaxants to prevent excessive potentiation of their action. This is because lithium's effect on the neuromuscular junction can last for 24 hours after its discontinuation, increasing the risk of prolonged muscle relaxation and respiratory depression.

**Why Each Wrong Option is Incorrect**

* **Option A:** 2 days before administration of the muscle relaxant is incorrect because lithium's effect on the neuromuscular junction may still be present after 2 days, increasing the risk of excessive potentiation.
* **Option B:** 1 day before administration of the muscle relaxant is incorrect because it may not be enough time for lithium to be completely cleared from the system, increasing the risk of prolonged muscle relaxation.
* **Option C:** 3 days before administration of the muscle relaxant is incorrect because it is not a standard recommendation and may not be necessary in most cases.

**Clinical Pearl / High-Yield Fact**
It is essential to note that lithium and non-depolarizing muscle relaxants should be used with caution and in a controlled setting, as their combination can lead to prolonged muscle relaxation and respiratory depression.

**Correct Answer:** C. 2 days before administration of the muscle relaxant should lithium be stopped.