**Core Concept**
Autosomal dominant inheritance is a type of genetic transmission pattern where a single copy of the dominant allele is sufficient to cause the expression of the trait or disease. This occurs when one of the two copies of the gene is mutated, leading to the manifestation of the disorder.

**Why the Correct Answer is Right**
In autosomal dominant inheritance, each parent contributes one allele to the offspring. If one parent is affected and has the dominant allele, there is a 50% chance that the offspring will inherit the mutated allele and be affected. This is because the affected parent has two alleles, one of which is the mutated dominant allele. The unaffected parent, being a carrier of the recessive allele, has a 50% chance of passing it to the offspring. Therefore, the offspring has a 50% chance of inheriting the mutated dominant allele from the affected parent and a 50% chance of inheriting the recessive allele from the unaffected parent.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it incorrectly states that 25% of the offspring will be affected and 50% will be carriers. In autosomal dominant inheritance, the offspring will either inherit the dominant allele and be affected or inherit the recessive allele and be a carrier, with no combination of both.
**Option B:** This option is incorrect because it incorrectly states that 50% of the offspring will be affected and 75% will be carriers. In autosomal dominant inheritance, the offspring will either inherit the dominant allele and be affected or inherit the recessive allele and be a carrier, but not both.
**Option C:** This option is incorrect because it states that 75% of the offspring will be affected, which is not true in autosomal dominant inheritance. The correct probability is 50% affected and 50% unaffected.

**Clinical Pearl / High-Yield Fact**
In autosomal dominant inheritance, the presence of a single copy of the dominant allele is sufficient to cause the expression of the trait or disease. This is in contrast to autosomal recessive inheritance, where two copies of the recessive allele are required to manifest the disorder.

✓ Correct Answer: D. 50% affected, if one parent affected