This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General, Subject name: Microbiology
Z-value of an organism: 
Select and explain. 
A. The time required to kill 90% of cells at a particular temperature, B. The time required to kill all cells at a particular temperature, C. Is the temperature change required for the D-value to change by a factor of ten, D. Is the temperature change required for the D-value to change by a factor of five
C: Is the temperature change required for the D-value to change by a factor of ten
Answer: C: Is the temperature change required for the D-value to change by a factor of ten 
Explanation: Ans. C. Is the temperature change required for the D-value to change by a factor of tena. D value of an organism is the time needed at a certain temperature to kill 90% of the organisms in the medium,b. Z-value of an organism is the temperature change required for the D-value to change by a factor of ten