All the three affects the resistance....
Resistance R=resistivity X (length/area)
so here we can see that the first two options affects the resistance straight.
But in an ordinary conductor when temperature changes it changes the resistivity of the conductor and thus affect the resistance indirectly.
Usually in an ordinary conductor resistance is seen to increase with temperature...Its interesting to note that we can even make zero resistance this way(super conductors) by making the temperature very low(about zero kelvin).
