**Core Concept**
The deltoid ligament, also known as the medial ligament of the ankle, is a strong, fan-shaped ligament that provides medial stability to the ankle joint. It is composed of four distinct bands: the tibionavicular, tibiocalcaneal, posterior tibiotalar, and anterior tibiotalar bands.

**Why the Correct Answer is Right**
The deltoid ligament is attached to the medial malleolus of the tibia, which is a bony prominence that forms the medial aspect of the ankle joint. The ligament also attaches to the medial aspect of the talus, specifically the sustentaculum tali, a bony projection that supports the talus. Additionally, the spring ligament, also known as the plantar calcaneonavicular ligament, is a ligament that supports the head of the talus and is closely associated with the deltoid ligament. However, the medial cuneiform is a bone in the midfoot and is not a normal attachment site for the deltoid ligament.

**Why Each Wrong Option is Incorrect**
**Option A:** The medial malleolus is indeed a normal attachment site for the deltoid ligament, making this option incorrect.
**Option C:** The spring ligament is closely associated with the deltoid ligament and is not an incorrect attachment site.
**Option D:** The sustentaculum tali is a normal attachment site for the deltoid ligament, making this option incorrect.

**Clinical Pearl / High-Yield Fact**
The deltoid ligament is an important structure to identify in ankle injuries, as it can be torn or sprained, leading to medial instability of the ankle joint. A high-arched foot or a history of ankle instability may increase the risk of deltoid ligament injuries.

**✓ Correct Answer: B. Medial cuneiform**