Option C is wrong because The kernel level threads are independent to each other and they have more number of contexts than User level thread. And the context switching time depends on the number of contexts. Also To give switch the thread in Kernel ,they required System Calls made to Operating System. And hence Kernel Level Threads require more Time than User level thread.
Option C is false statement
Option A is also False because CPU utilization does not increase ALWAYS. At some point ,on increasing DOM(Degree of Multiprogramming) The CPU utilization decreases and This phenomenon is called THRASHING.
So none of them is true
CORRECT ME IF WRONG