Answer: A register that stores the address of the next instruction to be executed
Explanation: Program counter is register of the CPU(central processing unit) .It contains the memory address of the instruction that is to be executed in next turn after the present instruction is executed.This is also known as the instruction pointer .The cycle followed by the counter is fetch ,decode and execute.
Other options are incorrect because it does not store next instruction,does not count number of instruction or stores the memory for reading and writing.It also does not act as a control circuit.