Heat travels in slow convection currents of solid materials within Earth's mantle. Heat that rises in these currents A.
is a by-product of frictional forces between Earth's tectonic plates as they slide past one another.
B.
is provided externally by gravitational energy in the Solar System.
C.
is a by-product from the decay of Earth's radioactive isotopes.
D.
is provided externally by the Sun.

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.

the answer would be   10%

the answer is true when observing or determining population size, a direct observation is use, in which each organism is counted in a population or in an area. one benefit of this measure is that you get the exact population count but it will take a long time to  determine  the  size  of a  population.

the circumference of the solar disc is 4375246 km, nearly.

explanation: