**Core Concept**
Lignocaine with epinephrine is a local anesthetic agent used for various procedures. The combination of lignocaine and epinephrine allows for a higher dose of lignocaine to be administered safely, as epinephrine helps to reduce bleeding and prolong the duration of anesthesia.

**Why the Correct Answer is Right**
The maximum recommended dose of lignocaine with epinephrine is 7 mg/kg without upper limit of total dose. This is because epinephrine helps to reduce the systemic absorption of lignocaine, thereby reducing the risk of systemic toxicity. The epinephrine also helps to constrict blood vessels, which reduces bleeding and prolongs the duration of anesthesia.

**Why Each Wrong Option is Incorrect**
**Option A:** This is incorrect because there is no evidence to support a lower dose limit for lignocaine with epinephrine.
**Option B:** This is incorrect because the maximum dose is not related to the concentration of lignocaine.
**Option C:** This is incorrect because the maximum dose is not related to the volume of lignocaine administered.

**Clinical Pearl / High-Yield Fact**
When using lignocaine with epinephrine, it's essential to note that the maximum dose is based on the total amount of lignocaine administered, not the concentration or volume.

**Correct Answer: D. 7 mg/kg.**