**Core Concept**
Type 1 diabetes is a chronic autoimmune disease characterized by the selective destruction of pancreatic beta cells responsible for insulin production. The destruction of beta cells leads to absolute insulin deficiency, resulting in hyperglycemia.

**Why the Correct Answer is Right**
The destruction of beta cells in type 1 diabetes is a gradual process, occurring over several years. Studies have shown that by the time type 1 diabetes becomes evident, approximately 80-90% of the original beta cell mass has been destroyed. This destruction is primarily mediated by autoreactive T-cells that recognize and target beta cells as foreign. The remaining beta cells are often insufficient to maintain normal glucose homeostasis, leading to the characteristic hyperglycemia of type 1 diabetes.

**Why Each Wrong Option is Incorrect**
**Option A:** 30% - This option underestimates the extent of beta cell destruction that occurs in type 1 diabetes. While some individuals may have residual beta cell function, 30% destruction is not sufficient to explain the development of type 1 diabetes.
**Option B:** 50% - This option also underestimates the extent of beta cell destruction. Studies have consistently shown that more than 50% of beta cell mass is destroyed by the time type 1 diabetes becomes evident.
**Option C:** 95% - This option overestimates the extent of beta cell destruction. While the majority of beta cell mass is destroyed, a small number of residual beta cells may remain, contributing to the variability in disease presentation.

**Clinical Pearl / High-Yield Fact**
In type 1 diabetes, the residual insulin production can lead to a phenomenon known as "honeymoon phase," where blood glucose levels may temporarily normalize due to the remaining beta cell function. However, this phase is often short-lived, and insulin replacement therapy is eventually required to maintain glucose homeostasis.

**Correct Answer: C. 85%**