Physics
When a piece of pure silicon is doped with aluminium, then

The doped silicon piece will become n-type
The conductivity of the doped silicon piece will remain the same
The doped silicon piece will become p-type
The resistivity of the doped silicon piece will increase

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Physics
Inside an aeroplane, flying at a high altitude,

normal humidity and partial vacuum are maintained.
normal atmospheric pressure is maintained by the use of air pumps.
the pressure inside is less than the pressure outside.
the pressure is the same as that outside.

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