Assertion: Evolutionary trend is continous changes of character in a linage.
Reason: Lineage is an evolutionary sequence arranged in linear order.

Explanation

To analyze the assertion and reason provided in the question, we can break down the statements and evaluate their validity step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Evolutionary trend is a continuous change of character in a lineage."
- This means that over time, as organisms evolve, we observe gradual changes in their characteristics. This is indeed a fundamental concept in evolutionary biology, where traits can shift due to various factors, including natural selection.

2. **Evaluating the Reason**:
- The reason states that "Lineage is an evolutionary sequence arranged in linear order."
- This implies that lineage refers to the direct ancestral line from one generation to the next, showing how species evolve over time. This definition is also accurate in the context of evolutionary biology.

3. **Determining the Relationship**:
- While both the assertion and reason are true, the reason does not provide an explanation for the assertion. The assertion discusses the concept of evolutionary trends, while the reason merely defines what a lineage is without linking it back to the assertion about continuous change.

4. **Conclusion**:
- Since both statements are true but the reason does not explain the assertion, we conclude that the correct answer is option B: "Assertion and reason both are true but reason is not an explanation of the assertion."