**Core Concept**
Dacrocystorhinostomy (DCR) is a surgical procedure aimed at relieving nasolacrimal duct obstruction by creating a new passage for tear drainage from the lacrimal sac to the nasal cavity. This procedure involves the creation of a new opening between the lacrimal sac and the nasal cavity.

**Why the Correct Answer is Right**
The correct answer involves the anatomical structure of the lacrimal apparatus. During DCR, the surgeon creates a new ostium (opening) in the lacrimal sac, which is then connected to the nasal cavity. This connection is established through the anterior ethmoidal bone, allowing for the free flow of tears into the nasal cavity. The lacrimal sac is located in the lacrimal fossa of the medial orbital wall, adjacent to the anterior ethmoidal bone.

**Why Each Wrong Option is Incorrect**
**Option A:** This option does not specify the correct location of the new ostium in the lacrimal sac.
**Option B:** This option is incorrect as the lacrimal sac is not directly connected to the paranasal sinuses.
**Option C:** This option is incorrect as the lacrimal sac is not opened into the orbit.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that DCR is a procedure of choice for patients with nasolacrimal duct obstruction who have failed conservative management or have symptoms of chronic dacryocystitis.

**Correct Answer: D. The anterior ethmoidal bone.**