The phrase "a ribbon at a time" is an expression that is not specifically related to the rising of the Sun. However, it can be interpreted as a metaphorical way of describing a slow and gradual process. In this case, it is being used to describe the Sun rising slowly and gradually.

- Metaphorical Meaning:
The phrase "a ribbon at a time" is a metaphor that compares the gradual process of something to the slow and steady unrolling of a ribbon. Just as a ribbon unrolls one section at a time, a process or event unfolds gradually, step by step. The phrase suggests that patience and persistence are required in order to achieve a desired outcome.

- The Sun Rises Slowly and Gradually:
When applied to the rising of the Sun, the phrase implies that the Sun's ascent is not sudden or abrupt, but rather occurs gradually over time. This aligns with our observation that the Sun appears to rise gradually in the morning, starting from the horizon and slowly moving higher in the sky. The phrase captures the idea that the Sun's rising is a process that unfolds gradually, rather than happening instantaneously.

- Implication of the Answer:
By choosing option 'A', it suggests that the Sun does not rise in a straight line, spiral motion, or abruptly. Instead, it rises slowly and gradually, akin to the unrolling of a ribbon. This interpretation aligns with the common understanding of how the Sun rises in the morning.

In conclusion, the phrase "a ribbon at a time" is a metaphorical expression that describes a slow and gradual process. When applied to the rising of the Sun, it implies that the Sun's ascent is not sudden or abrupt but occurs slowly and gradually. Therefore, option 'A' is the correct answer.