Final answer:
The sounds that convey the gentleness of sleep in the poem "To Sleep" are words that contain the letters "m" and "s", which create a soft and soothing effect.
Step-by-step explanation:
The sounds in the poem "To Sleep" that convey the gentleness of sleep are best represented by words that contain the letters "m" and "s." The softness of these consonants can mimic the soothing and hushed qualities of sleep. For example, in poetry and prose, the repeated 's' sounds, often associated with terms like 'soft,' 'sleep,' and 'silence,' can create a gentle lulling effect that mirrors the tranquility of sleep. Similarly, the 'm' sound is known as a nasal consonant, giving it a soft and muffled quality, which is also evocative of the quietude and gentleness associated with sleep, heard in words such as 'calm' or 'dream.'