Final answer:
The fraction of the iron anchor's weight supported by the buoyant force when submerged in saltwater depends on the density of the anchor and the density of the saltwater.
Step-by-step explanation:
When an object is submerged in a fluid, it experiences a buoyant force that opposes its weight. This buoyant force is equal to the weight of the fluid displaced by the object. The fraction of the iron anchor's weight that will be supported by the buoyant force can be found by comparing the density of the iron anchor to the density of saltwater. If the density of the iron anchor is greater than the density of saltwater, the anchor will sink and the buoyant force will be less than the weight of the anchor. On the other hand, if the density of the iron anchor is less than the density of saltwater, the anchor will float and the buoyant force will be equal to the weight of the anchor.
In this case, since the anchor is made of iron which has a density greater than that of saltwater, the anchor will sink. Therefore, the fraction of its weight supported by the buoyant force will be less than 1. None of the provided answer options accurately represent the fraction of the iron anchor's weight supported by the buoyant force when submerged in saltwater.