Lithium is softer than ...... but harder than other alkali metals.

Explanation

To solve the question, we need to analyze the properties of lithium in comparison to other alkali metals and some other metals.

### Step-by-Step Solution:

1. **Understanding Alkali Metals**:
- Alkali metals include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). They are known for being soft and having low melting points.

2. **Comparing Lithium with Other Metals**:
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