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.
Finding focus: before writing and during revision. A critical factor in establishing a focus is setting a goal. Studies by writing researchers show that goal-setting is an important element of planning for mature adult writers (Bereiter and Scardamalia, 1987; Hayes and Flower, 1980).