Final answer:
Styrofoam cup and pencil are likely to float in water as they are less dense than water, making option 4) the correct answer. The ability of objects to float or sink in water is primarily determined by their density in comparison to that of water.
Step-by-step explanation:
Objects that are less dense than water will float, while those with a higher density will sink. A spoon and scissors are typically made of metal, which is denser than water, so they are likely to sink. A pencil may float because it is made of wood, which is less dense than water. Of all the options, styrofoam is known for being much less dense than water, and so both a styrofoam cup and a pencil are likely to float on water due to their lower densities.
Thus, the correct answer is: 4) styrofoam cup and pencil.
It is important to remember factors such as shape and surface area can also affect an object's buoyancy, along with its density relative to the water. For example, a steel needle can float when placed carefully on water due to the surface tension of the water providing enough support to counteract its density.