Answer: The weakest is "rubbing alcohol", the next strongest is "water with detergent", after that "water", and the strongest is "corn oil". The unknown is likely water (or possibly corn oil).
Step-by-step explanation:
Remember that liquids are just a collection of lots of tiny molecules jiggling around. In the experiment, we are testing the strength of the intermolecular forces (the strength of the "glue" that holds molecules together) by seeing how many paper clips (how much weight) they can hold before breaking.
Rubbing alcohol couldn't hold any paper clips, so it's "glue" must be very weak. That is, the intermolecular forces of rubbing alcohol are very weak.
Water with detergent did a little better; it could hold 3 paper clips before the "glue" broke. The intermolecular forces of water with detergent are stronger than those of rubbing alcohol.
Water is pretty strong. It could hold 5 paper clips before the "glue" finally broke. The intermolecular forces of pure water are stronger than those of water with detergent added. (This suggest that the detergent actually makes the water "weaker" in some way!)
The strongest of all the liquids was corn oil. It could hold 8 paper clips before it finally broke. The intermolecular forces of corn oil are the strongest of all liquids tested.
In summary:
Rubbing Alcohol < Water with detergent < Water < Corn Oil.
Regarding the mystery liquid (I'm assuming you were given a bottle containing an unknown substance and performed the same paper clip test): The unknown liquid was able to hold 6 paper clips before the "glue" broke, so it's most similar to water. Why did it hold more than 5 this time? Perhaps your technique improved on bottle B, or maybe you had bad luck on the original water sample.