Read the following statements carefully
*Y : The resistivity of semiconductor decreases with increase of temperature.*
*Z : In a conducting solid, the rate of collisions between free electrons and ions increases with increase of temperature.*
Select the correct statement (s) from the following
(a) Y is true but Z is false
(b) Y is false but Z is true
(c) Both Y and Z are true
(d) Y is true and Z is the correct reason for Y