What do you believe will be the single most important demographic issue with which the world must cope over the next half century, and how do you think this issue should be dealt with?

d. they are naturallyoccuring inorganic fuels like coal and petroleum.

1."lessen the worth of ."

2."increase the worth of."

3." beyond the worth of."

4."against the worth of ."

a mid-ocean ridge or mid-oceanic ridge is an underwater mountain range, formed by plate tectonics. this uplifting of the ocean floor occurs when convection currents rise in the mantle beneath the oceanic crust and create magma where two tectonic plates meet at a divergent boundary.a geomagnetic reversal is a change in a planet's magnetic field such that the positions of magnetic north and magnetic south are interchanged.