The Correct Answer is Option B: wide enough.

Explanation:
To understand why option B is the correct answer, let's break down the sentence and analyze the different options.

The sentence states: "This bed is not ---- for two people to sleep in."

1. Option A: wide as
- This option is grammatically incorrect. The correct phrase would be "wide as the bed," but this does not fit the context of the sentence.

2. Option B: wide enough
- This option is grammatically correct and fits the context of the sentence. "Wide enough" implies that the bed is not sufficiently wide for two people to sleep in comfortably.

3. Option C: wider than
- This option is grammatically incorrect. The sentence does not make a comparison between the bed and anything else to indicate that it is wider than something.

4. Option D: too wide
- This option is grammatically incorrect. The phrase "too wide" implies that the bed is excessively wide, which contradicts the context of the sentence. The sentence states that the bed is not suitable for two people, suggesting that it is not wide enough.

5. Option E: the widest
- This option is grammatically incorrect. "The widest" implies that the bed is the widest among multiple beds, but the sentence does not provide any basis for comparison.

Therefore, the correct answer is option B: wide enough. This option effectively conveys that the bed is not of sufficient width for two people to sleep in comfortably.