What is the difference between a density-dependent and a density-independent limiting factor?

What causes the force that pushes magma from the magma chamber through the pipe and vent of a volcano?

The human genome project is devoted to mapping the general dna sequence of our species. this could lead to the development of new medicines, as well as the possibility of using gene therapy to treat certain diseases. however, there are some ethical issues surrounding the mapping of individual genomes. one concern is a) that your genes may change over time, making the project useless. b) that insurance companies could discriminate based on genetic make-up. c) that since this has never been done before, we should probably not do it now. d) that sequencing our individual genomes is so expensive, it is a counter-productive strategy.

Fill in the blank with the correct sphere label. a: ⇒ geosphere b: ⇒ biosphere c: ⇒ hydrosphere