Final answer:
The most accurate answer for the shape of the histogram and the class interval containing the median, given a symmetrical distribution, is option (a): The histogram is bell-shaped, and the median is in the class interval 20-30.
Step-by-step explanation:
Based on the information provided, it is clear that we are discussing a symmetrical distribution - typically represented by a bell-shaped curve. In a bell-shaped or normal distribution, the mean, median, and mode all fall at the same point. This is highlighted in the example where the mean, the median, and the mode for the given data are each seven, indicating a symmetrical distribution. If the histogram is symmetrical and bell-shaped, and given that the median is the middle value of a data set, it would logically be located in the central class interval of the distribution.
Considering this, option (a) states: 'The histogram is bell-shaped, and the median is in the class interval 20-30.' If the histogram is indeed bell-shaped, as per the information, then this option correctly describes the shape of the histogram and the interval containing the median. Options (b), (c), and (d) describe other shapes of distributions and are not consistent with the information that indicates a bell-shaped, symmetrical pattern wherein the mean and the median align.
Therefore, the most accurate answer based on the symmetrical distribution described would be option (a).