In the following passage, some words have been deleted. Read the passage carefully and select the most appropriate option to fill in each blank.
Mirrors (1) ________ used since ages. It is said that Archimedes used huge mirrors to focus the heat of the sun’s rays on enemy ships to burn them. The same (2) _______ is used in solar cookers, where mirrors are used to reflect and focus the sun’s rays onto cooking containers. Astronomers use huge concave mirrors to focus starlight. The mirrors used in telescopes are polished by giving a thin coat of silver or aluminium to the glass. With telescopes, astronomers can see the heavenly bodies, but even without the telescopes, one can see the moon. A full moon shining (3) ________ is a beautiful sight. But it is also a puzzle, because if the sun and the moon both give the same light, then why is the moonlight more pleasant? The reason is that the moon reflects very (4) ______ sunlight, in fact, only seven percent of the light it receives. The earth reflects about half of the radiation that it receives from the sun. Imagine how bright the earth must be looking from the moon! One can even read a book on the moon in the earthlight. However, you do not have to travel all the way to the moon to realize how strong the Earth's light is. Observe the crescent moon soon after the new moon. The bright crescent is illuminated by the sun. The rest of the moon is illuminated by earthlight. In other words, the light reflected by the earth is falling on the moon. This is being reflected back to us and is strong enough to show the moon (5) _______. As the crescent increases in size, this effect disappears.
Select the most appropriate option to fill in blank number 5.