Step-by-step explanation:
Resistance is defined as the ability of a substance to resist the flow of current through the substance. Formula to calculate resistance is as follows.
R =
As outer surface of a wire is in the shape of sphere. therefore, its area will be as follows.
A =

or, A =

where, d = diameter of the sphere
This means that with increase in diameter of a conductor there will occur an increase in area of the wire. As area is inversely proportional to resistance so, increase in area will lead to a decrease in resistance.
On the other hand, relation between resistivity and temperature is as follows.

where,
= resistivity
d = mean free path of electrons
A = amplitude of atomic vibrations
T = temperature
Also, resistivity is directly proportional to resistance. So, with increase in temperature there will occur an increase in resistance of the conductor.
Thus, we can conclude that only technician B is correct.