When S-type/R-type of Diplococcus is injected into mouse, the mouse will die.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Strains of Diplococcus:**
- Diplococcus pneumoniae has two strains: S-type (smooth) and R-type (rough).
- The S-type is pathogenic, meaning it can cause disease, while the R-type is non-pathogenic.

2. **Characteristics of S-type and R-type:**
- The S-type has a capsule that protects it from the host's immune system, allowing it to cause infections.
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