The correct answer is - D. A drought kills all the plants in an area, leaving bare land.
If there's such a big drought that will manage to kill off all the vegetation in an area and leave bare land behind it, than the land will be degraded in no time. Once the land is left without its natural protection that the roots of the vegetation provide, the land will be exposed to high rates of and erosion. The erosion will be very quick and the top layers of the soil will be moved away with every wind and rainfall that will appear. That will degrade the land to a very high degree, making it totally unusable and it will need lot of time to eventually recuperate.
Ribozymes are biochemically too complex to have ever produced themselves naturalistically. They are an intermediate cellular functioning assembly that cannot survive on its own and they are too restrictive in function to enable metabolism and reproduction at the level of criticality to be considered plausible for life.
Their simplicity relative to RNA and DNA make them an attractive possibility, but they are not strategic enough, robust enough or in any producible using naturalistic processes.
Stem cells are cells of the body that can divide and become differentiated. stem cells specialise and take specific functions when an organism grows
mature tissues such as muscle, blood, tissue, bone, nerves, liver all have different types of cells.
they come from three to five day old embryo cells.
they represent potential in the regeneration and repair of damaged tissue. some therapies actually currently use stem cells for this reason
Your answer is C.Calcium.
Hope this helps :)
