Hard to say from the pic as you can’t see where the loose wire connects at the battery terminal. If the starter does not crank, it is probably the starter cable, but can‘t say with 100% certainty. Follow the cable to see where it leads. Also, look at the broken cable to see if it has a red stripe - I believe that would identify the cabe as leading to the starter. The battery positive terminal will have at least two wires - a thick wire that goes straight to the starter, and a smaller cable going to the fuse panel. A third wire may go to a relay or other aftermarket component.