1. the point in the moon's orbit when it's farthest away from the earth is called
a. perigee.
b. penumbral.
c. apogee.
d. eclipse.
2. which type of electromagnetic radiation cannot be focused?
a. ultraviolet
b. x-rays
c. infrared
d. gamma rays
3. which of the following statements is true of the corona?
a. it's where sunspots occur.
b. it's the outermost layer of the sun's atmosphere.
c. it's the visible surface of the sun.
d. it's responsible for the sun's density.
4. tides are a result of
a. currents in the ocean.
b. strong winds in the equatorial regions.
c. friction caused by the earth's rotation.
d. the gravitational attraction of the sun and moon.

1.C

2.D

3.B

4.D

Explanation:

1. The orbit on which moon revolve around earth has a perigee point which is the nearest point to earth while apogee is the farthest point to planet earth.  

A penumbral is a region in which occluding body obscure a portion of light. It has no relation with the moon's orbit. Also an eclipse is a phase based on position of moon with respect to earth and sun

Hence, option C is correct

2. Gamma rays are extremely powerful and energetic as they are produced as a result of radiation and hence it is very difficult to focus them on normal lenses which are designed to focus only visible light. They interact with the matter of the focusing surface and destroys them selves.

Hence, option D is correct

3. Corona is the outer surface of stars  that extends to millions of kilometers into the space. Sun being a star has corona at its outer layer which is visible only during  

total solar eclipse. Hence option B is correct

4. When the gravitational force of moon attracts the water on earth, it presume a rising and falling form that is termed as tides.  

Hence option D is correct