单项选择题

Oh! I have just had such a lovely dream!
And then I woke,
And all the dream went out like kettle-steam,
Or chimney-smoke.
My dream was all about -- how funny, though!
I’ve only just
Dreamed it, and now it has begun to blow
Away like dust.
In it I went -- no! In my dream I had --
No, that’s not it!
I can’t remember, oh, it is too bad,
My dream a bit.
But I saw something beautiful, I’m sure--
Then someone spoke,
And then I didn’t see it any more,
Because I woke.
What do we do every night, whether we know it or not We dream. Researchers have found that We dream about the same amount on nights that we remember our dreams as on the nights that we don’t. The amount of time we sleep is broken into cycles and states. There are two states of sleep:
The first state, is called NREM, or non-rapid eye movement. It consists of four stages: Stage 1 is when we feel relaxed and sleepy. Stage 2 is when we move into a light sleep. We don’t dream in these two stages. Stages 3 and 4 are called slow-wave sleep. In these stages, we are in a deep sleep and the dreams we have are ones we don’t usually remember.
The second state is called REM, or rapid eye movement. This is when we dream the most and have the dreams we remember the most. For many people, their REM dreams are the most meaningful and visually exciting. Approximately three-fourths of our total sleep time is spent in the NREM state and one-fourth in the REM state. We sleep by cycling through these states. Throughout the night, we experience four to six NREM/REM cycles.

The dream experienced in the poem most likely occurred during ().

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