**Core Concept**
An inclined plane is a type of orthodontic appliance used to correct malocclusions by applying a gentle, continuous force to the teeth. In orthodontics, an inclined plane is often employed to treat Class II malocclusions, which are characterized by an overbite.

**Why the Correct Answer is Right**
In the treatment of a developed crossbite, an inclined plane is used to correct the malalignment of the teeth. A developed crossbite occurs when the upper teeth bite inside the lower teeth, often resulting from a Class III malocclusion. The inclined plane appliance is designed to move the upper teeth distally (outward) and the lower teeth mesially (inward), thereby correcting the crossbite. This is achieved by applying a gentle, continuous force to the teeth, which promotes bone remodeling and tooth movement.

**Why Each Wrong Option is Incorrect**
**Option A:** A developing crossbite refers to a Class III malocclusion in which the lower teeth bite inside the upper teeth. In this scenario, an inclined plane would not be used to correct the malocclusion.
**Option C:** A deep bite is characterized by an overclosure of the lower jaw, where the upper teeth bite too far down into the lower teeth. An inclined plane is not typically used to treat deep bites.
**Option D:** An open bite is a type of malocclusion where the upper and lower teeth do not meet, resulting in a gap between the teeth. Inclined planes are not used to treat open bites, as they would not be effective in closing the gap between the teeth.

**Clinical Pearl / High-Yield Fact**
When using an inclined plane in the treatment of a developed crossbite, it is essential to monitor the patient's progress closely to avoid overcorrection, which can lead to an unstable occlusion.

**✓ Correct Answer: B. Developed cross bite**