Which of the following phrases illustrates the concept of onomatopoeia?

Onomatopoeia refers to words that phonetically imitate or resemble the sound that they describe. In this case, the phrase "The clock tick-tocked" effectively demonstrates this concept through the use of the words "tick" and "tock." These words mimic the actual sound that a clock makes, providing a vivid auditory image that enhances the description.

The other phrases do not exhibit onomatopoeic qualities. For instance, stating "The sun was shining brightly" does not involve any sound representation. Similarly, "She is like a rose" employs a simile to draw a comparison, while "He runs as fast as a cheetah" uses another simile to compare speed but does not evoke sound. Therefore, "The clock tick-tocked" stands out as the phrase that perfectly exemplifies onomatopoeia.