User: The greenhouse effect is a result of A. absorption and radiation of energy in the hydrosphere. B. consumption of fruits and vegetables that produce a biofuel. C. absorption and radiation of energy in the atmosphere.
A principal focus or focal point is a special focus: 1  For a lens, or a spherical or parabolic mirror, it is a point onto which collimated light parallel to the axis is focused. Since light can pass through a lens in either direction, a lens has two focal pointsâone on each side.
Focus is the topic/subject established by the writer in response to the writing task. The writer must clearly establish a focus as he/she fulfills the assignment of the prompt. If the writer retreats from the subject matter presented in the prompt or addresses it too broadly, the focus is weakened.