Last year all refuse collected by Shelbyville city services was incinerated. This incineration generated a large quantity of residual ash. In order to reduce the amount of residual ash Shelbyville generates this year to half of last year's total, the city has revamped its collection program. This year city services will separate for recycling enough refuse to reduce the number of truckloads of refuse to be incinerated to half of last year's number.

Which of the following is required for the revamped collection program to achieve its aim?

(A) This year, no materials that city services could separate for recycling will be incinerated.
(B) Separating recyclable materials from materials to be incinerated will cost Shelbyville less than half what it cost last year to dispose of the residual ash.
(C) Refuse collected by city services will contain a larger proportion of recyclable materials this year than it did last year.
(D) The refuse incinerated this year will generate no more residual ash per truckload incinerated than did the refuse incinerated last year.
(E) The total quantity of refuse collected by Shelbyville city service's this year will be no greater than that collected last year.

The correct option is D

Explanation:

Cutting the number of truckloads of refuse in half must reduce the amount of residual ash by half of last year's level. However, if the removal of the recycled refuse does not proportionately reduce the amount of ash, this will not happen.

So, the answer D states a requirement for the collection program to achieve its aim.

D) The refuse incinerated this year will generate no more residual ash per truckload incinerated than did the refuse incinerated last year.  IF THE WHOLE POINT OF THE PROGRAM IS TO REDUCE THE AMOUNT OF RESIDUAL ASH, THEN IT IS IMPORTANT TO CHECK IF CUTTING THE TRUCKLOADS OF WASTE BY HALF ACTUALLY CUTS RESIDUAL ASH BY HALF.  

Explanation:

Other options are wrong because:

sound is invisible, but sometimes we can feel it. when a kettle-drum is thumped with a stick that time the tight drum skin moving up and down very quickly for some time and then it pumped sound waves into the air. loudspeakers also work in a similar manner.

components of a speaker:

electromagnet

in order to translate an electrical signal into an audible sound, an electromagnet is used in looudspeakers

  suspension

suspension is used to   center the voice coil in the gap of the magnet and it exerts a restoring force to keep it there. suspension is used to limits the maximum mechanical excursion of the diaphragm and voice coil.

voice coil

voice coil is a coil of wire which is attached to the apex of a loudspeaker cone. it provides the motive force to the cone by the reaction of a magnetic field to the current passing through it.

cone

in a   loudspeaker, a   thin, semi-rigid membrane attached to the voice coil, which moves in a magnetic gap due to which it vibrates   and produced sound. it is known as diaphragm and it can also be called a cone, though not all speaker diaphragms are cone-shaped.

surround

surround is also known as front suspension. surround is used to join the cone to the chassis. together with the suspension it controls the cone excursion, and it is also used to   determine how energy which is   travelling through the cone is absorbed, and how the speaker limits when it reaches the ends of its travel.

dustcap

dustcap is used to protect the voice coil from dust and dirt. it is a part of the cone.

how speaker work

the outer part of the cone is fastened to the outer part of the loudspeaker's circular metal rim. the inner part is fixed to   voice coil that sits just in front of a permanent magnet . when loudspeaker is hooked up to a stereo, electrical signals feed through the speaker cables into the coil. it will convert the coil into an electromagnet magnet . when electricity flows back and forth in the cables, the electromagnet either repels or attract the permanent magnet. this moves the coil back and forth, and it pull and push the loudspeaker cone. like a drum skin vibrating back and forth, the moving cone pumps sounds out into the air.in this way loudspeakers works.

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