Read the following statements carefully
`Y`: The resistivity of semiconductor decreases with increases of temperature.
`Z`: In a conducing solid, the rate of collisions between free electrons and joins increases with the 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 `Z` and `Z` is the correct reason for `Y`

Explanation

Resistivity of conductors increases with increase in temperature because rate of collisions between free electrons and ions increase with increase of temperature. However the reistivity of semiconductors decreases with increase in temperature, because more and more covalent bonds are broken at higher temperatures and free electrons increase with increase in temperature. Therefore, the correct option is (c).