Context: A key component common to all CPUs is the program counter, a special memory cell (a register) that keeps track of which location in memory the next instruction is to be read from.

Question: A special memory cell of a CPU is called what?
Answer: a register

Question: A register of a CPU keeps track of what?
Answer: which location in memory the next instruction is to be read from

Question: What is a component that all CPUs have?
Answer: the program counter