The question presents a situation with four possibilities:

1. Guests who only ate fish.

2. Guests who only ate meat.

3. Guests who ate nothing because they were vegetarians and abstain from both fish and meat.

4. Guests who ate both fish and meat.

This can be represented by four distinct, mutually exclusive groups.

Option 1 presents four disjoint sets, each representing one group of guests, which will correctly reflect the situation. No overlaps between the sets are there which means no person belongs to more than one group.

Option 2, 3, and 4 won`t work.

Option 2 shows all groups overlap in some way, implying there is no way for someone to only eat fish or only eat meat.

Option 3 shows overlap between "meat only", "fish only" and "both" eaters, again this would not allow for guests to only eat one of the two food types.

Option 4 is incorrect as the "vegetarian" group overlaps with both the "meat only" and "fish only" groups, implying that there vegetarian guests are eating meat or fish, which is false.

Therefore, the correct answer is option 1.