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: Dental
Recently two methods of cPAP; conventional and bubble cPAP were compared. In the conventional method, 90 out of 160 showed extubation failure while 40 out of 160 showed extubation failure in bubble method, which test would be the best to compare the statistical significance between the rates of extubation failure in the two tests? 
Select and explain. 
A. Chi square test, B. Student's test, C. Paired t test, D. Analysis of variance
A: Chi square test
Answer: A: Chi square test 
Explanation: None