**Core Concept**
EMLA (Eutectic Mixture of Local Anesthetics) is a topical anesthetic cream used to numb the skin before various medical procedures. It contains a combination of two local anesthetics that work synergistically to provide effective analgesia.

**Why the Correct Answer is Right**
The correct answer, **B. Lidocaine + Prilocaine**, is a combination of two local anesthetics with distinct mechanisms of action. Lidocaine (a tertiary amine local anesthetic) blocks sodium channels, preventing the initiation and transmission of nerve impulses. Prilocaine (a secondary amine local anesthetic) also blocks sodium channels and has a higher lipid solubility than lidocaine, allowing it to penetrate the skin more easily. This combination of lidocaine and prilocaine in EMLA cream provides a rapid onset of action and a longer duration of analgesia.

**Why Each Wrong Option is Incorrect**
**Option A:** Lidocaine + Cocaine is not a commonly used combination in topical anesthetics. Cocaine is a vasoconstrictor and has sympathomimetic effects, which are not desirable in a topical anesthetic cream.
**Option C:** Lidocaine + Bupivacaine is not a typical combination in EMLA cream. Bupivacaine is a long-acting local anesthetic that is often used in regional anesthesia, but it is not suitable for topical application due to its high lipid solubility and potential for toxicity.
**Option D:** Bupivacaine + Prilocaine is not a recommended combination in topical anesthetics. Bupivacaine is a long-acting local anesthetic that can cause significant toxicity if absorbed systemically, and its combination with prilocaine may increase the risk of toxicity.

**Clinical Pearl / High-Yield Fact**
When using EMLA cream, it is essential to apply it correctly to ensure effective analgesia. The cream should be applied to the skin 1-2 hours before the procedure, and the area should be occluded with a dressing to enhance absorption.

**✓ Correct Answer: B. Lidocaine + Prilocaine**