A hypothesis is an educated guess, while a theory is usually a tested, well substained explanation of something.
pressure decreases<span> with increasing </span>altitude<span>. The </span>pressure<span> at any level in the atmosphere may be interpreted as the total weight of the </span>air<span> above a unit area at any </span>elevation<span>. At higher elevations, there are fewer </span>air<span> molecules above a given surface than a similar surface at lower levels.</span>
Dominant genes and recessive genes are both given to a parents offspring. However, not both can be expressed causing the difference of dominant and recessive. Dominant genes are more likely to be expressed and recessive genes are more likely to be repressed.
Since vectors are essentially quantities that have direction, D must be the answer as it contains a direction (down) while the other ones do not.