A reference frame can be moving. To make sure that newtons laws still apply, the reference frame must not be accelerating.
Weak winds that blow for short periods of time with a short fetch.
Today we can make observations that would lead us to the same conclusion as newton. If you throw a baseball in the air, it always comes back down. This is because of gravity. duh.
The text does not specify whether the resistance R of the wire must be kept the same or not: here I assume R must be kept the same.
The relationship between the resistance and the resistivity of a wire is

where

is the resistivity
A is the cross-sectional area
R is the resistance
L is the wire length
the cross-sectional area is given by

where r is the radius of the wire. Substituting in the previous equation ,we find

For the new wire, the length L is kept the same (L'=L) while the radius is doubled (r'=2r), so the new resistivity is

Therefore, the new resistivity must be 4 times the original one.