Which particles make up the nucleus of an atom?
a. protons and electrons
b. neutrons and electrons
c. protons only
d. protons and neutrons
e. neutrons only

D. Protons and neutrons.

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indicate valleys, hills, steepness and gentleness of slopes.

explanation:

contour lines on a map indicate elevation, or depth. numeric notations on contour lines refer to the level of elevation, or height about sea level.

conduction is the transfer of thermal energy (heat in transfer) due to collisions between the molecules in the object. collisions between adjacent atoms and molecules transfer kinetic energy from the warmer to the cooler object. the objects must be in physical contact.