This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Radiology
M in 99Tc"' stands for? 
Select and explain. 
A. Micro, B. Mega, C. Metastable, D. Metastatic
C: Metastable
Answer: C: Metastable 
Explanation: Metastable REF: Nuclear Physics: Principles And Applications by Lilley Page 20 "In 99Tcm the superscript M denotes that the technetium 99 is not in its ground state but a long lived metastable excited state"