**Core Concept**
Loeffler's serum slope is a type of growth medium used in microbiology to isolate and cultivate certain fastidious bacteria, such as Neisseria gonorrhoeae and Corynebacterium diphtheriae. It is a selective medium that supports the growth of these bacteria while inhibiting the growth of other microorganisms.

**Why the Correct Answer is Right**
Loeffler's serum slope typically contains nutrient broth, glucose, and horse serum, which provide the necessary nutrients for the growth of fastidious bacteria. However, it does not contain sheep blood, which is a common ingredient in other types of growth media, such as blood agar. The absence of sheep blood in Loeffler's serum slope is deliberate, as it can interfere with the growth of certain bacteria and make the medium less selective.

**Why Each Wrong Option is Incorrect**
**Option A:** Nutrient Broth is a crucial component of Loeffler's serum slope, providing a source of amino acids and other nutrients for bacterial growth.
**Option B:** Glucose is also an essential component of Loeffler's serum slope, serving as a primary energy source for the bacteria.
**Option C:** Horse serum is a key ingredient in Loeffler's serum slope, providing a source of proteins and other nutrients that support the growth of fastidious bacteria.

**Clinical Pearl / High-Yield Fact**
When working with Loeffler's serum slope, it's essential to remember that this medium is selective for certain fastidious bacteria and should not be used to isolate bacteria that require blood as a growth medium. This is a common exam trap, as some students may mistakenly include sheep blood in the list of ingredients for Loeffler's serum slope.

**✓ Correct Answer: D. Sheep blood**