**Core Concept**
Lilly's antidote is a medication used to counteract cyanide poisoning. It is a combination of three substances that work together to neutralize the toxic effects of cyanide on the body.

**Why the Correct Answer is Right**
Lilly's antidote, also known as Cyanokit, contains **sodium nitrite** (A), **amyl nitrite** (B), and **sodium thiosulfate** (C). These three substances work together to convert cyanide into a less toxic form that can be excreted by the body. Sodium nitrite and amyl nitrite induce methemoglobinemia, which binds to cyanide and forms a less toxic complex. Sodium thiosulfate then helps to convert this complex into thiocyanate, which is excreted by the kidneys. Dicobalt EDTA (D), on the other hand, is used as an antidote for cyanide poisoning but is not a component of Lilly's antidote.

**Why Each Wrong Option is Incorrect**
**Option A:** Sodium nitrite is actually a component of Lilly's antidote, not something it does not contain.
**Option B:** Amyl nitrite is also a component of Lilly's antidote and plays a crucial role in inducing methemoglobinemia.
**Option C:** Sodium thiosulfate is the third component of Lilly's antidote and is essential for converting cyanide into thiocyanate.

**Clinical Pearl / High-Yield Fact**
Dicobalt EDTA is another antidote for cyanide poisoning, but it is not used in Lilly's antidote. It is worth noting that both Lilly's antidote and dicobalt EDTA are used to treat cyanide poisoning, but they have different mechanisms of action and are used in different clinical scenarios.

**✓ Correct Answer:** D. Dicobalt EDTA