[A]: The colour of flowers in Bougainvillia is due to the coloured bracts.
[R]: The flowers of Bougainvillia are largest among the plant kingdom.

Options

A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true and R is false
D. If both A and R are false

Answer

To solve the question regarding the assertion and reason related to Bougainvillea, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "The colour of flowers in Bougainvillea is due to the coloured bracts."
- Bougainvillea is known for its vibrant colors, which are primarily due to the bracts (modified leaves) that surround the actual flowers. The true flowers are small and white, while the bracts can be magenta, pink, orange, or other colors.

2. **Evaluating the Reason**:
- The reason provided is "The flowers of Bougainvillea are largest among the plant kingdom."
- This statement is incorrect. The largest flowers in the plant kingdom are actually found in Rafflesia, not Bougainvillea. Bougainvillea flowers are relatively small compared to those of some other plants.

3. **Determining the Truth Values**:
- The assertion is true because the color of Bougainvillea is indeed due to the colored bracts.
- The reason is false because Bougainvillea does not have the largest flowers in the plant kingdom.

4. **Choosing the Correct Option**:
- Based on the evaluation, we find that the assertion is true and the reason is false. Therefore, the correct option is the third one: "if assertion is true and the reason is false."

### Final Answer:
The correct answer is: **Option 3** - Assertion is true and the reason is false.

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