90% of people marry there 7th grade l0ve. since u have read this, u will be told good news tonight. if u don't pass this on nine comments your worst week starts now this isn't fake. apparently if u copy and paste this on ten comments in the next ten minutes you will have the best day of your life tomorrow. you will either get kissed or asked out in the next 53 minutes someone will say i l0ve u this is irrelevent but idr.c
The last one is right answer i think
Fossil record in this case
Most fish (especially the "Bony fish") achieve neutral buoyancy through a sac called the swim bladder in there body of which is filled with air, not much but it'a just enough to keep then a float. The fish can control this organ, and using that they can fill or release air to allow them to rise or sink.
Cartilaginous fish however, do not have a swim bladder.
hope this helps :)