Part 1. Definition
You are given a passage. Using the information present in the passage, you need to classify it into one of the 10 topics: 0 - 'Society & Culture', 1 - 'Science & Mathematics', 2 - 'Health', 3 - 'Education & Reference', 4 - 'Computers & Internet', 5 - 'Sports', 6 - 'Business & Finance', 7 - 'Entertainment & Music', 8 - 'Family & Relationships', 9 - 'Politics & Government'.
Part 2. Example
Optical mice use an LED and a camera to rapidly
capture images of the surface beneath the mouse.
The infomation from the camera is analyzed by a
DSP (Digital Signal Processor) and used to detect
imperfections in the underlying surface and
determine motion. Some materials, such as glass,
mirrors or other very shiny, uniform surfaces
interfere with the ability of the DSP to
accurately analyze the surface beneath the mouse.

Since glass is transparent and very uniform, the
mouse is unable to pick up enough imperfections in
the underlying surface to determine motion.
Mirrored surfaces are also a problem, since they
constantly reflect back the same image, causing
the DSP not to recognize motion properly. When the
system is unable to see surface changes associated
with movement, the mouse will not work properly.
Answer: 4
Explanation: The passage talks about optical mice or mouse throughout which is a part of computer system. Thus, it is correctly classified to "Computers & Internet"
Part 3. Exercise
The answer is 9 stones (or maybe more).

After adding a look-alike to 9 stones, there will be 10. Name them ABCDEFGHIJ.

"ABC<DEF" means "the stones ABC as a group weigh less than the stones DEF."

Weighing 1. Weigh ABC vs. DEF.

If ABC<DEF:
--Weighing 2. Weigh ABC vs. GHI.
----If ABC<GHI, the look-alike must be light and among ABC.
----Weighing 3. Weigh A vs. B.
------If A<B, the look-alike is A.
------If A=B, the look-alike is C.
------If A>B, the look-alike is B.
----If ABC=GHI, the look-alike must be heavy and among DEF.
----Weighing 3. Weigh D vs. E.
------If D<E, the look-alike is E.
------If D=E, the look-alike is F.
------If D>E, the look-alike is D.

If ABC=DEF, the look-alike must be among GHIJ.
--Weighing 2. Weigh G vs. H.
----If G=H, the look-alike candidates are I and J.
----Otherwise, the look-alike candidates are G and H.
----Weighing 3. Weigh one of the two candidates against A.
------If they differ in weight, the look-alike is that candidate, otherwise it is the other candidate.

If ABC>DEF:
--Weighing 2. Weigh ABC vs. GHI.
----If ABC>GHI, the look-alike must be heavy and among ABC.
----Weighing 3. Weigh A vs. B.
------If A<B, the look-alike is B.
------If A=B, the look-alike is C.
------If A>B, the look-alike is A.
----If ABC=GHI, the look-alike must be light and among DEF.
----Weighing 3. Weigh D vs. E.
------If D<E, the look-alike is D.
------If D=E, the look-alike is F.
------If D>E, the look-alike is E.
Answer:
1