![](https://cos-cdn.shuashuati.com/pipixue-web/2020-1231-2005-12/ti_inject-812ce.png)
What conclusion can we come to, according to the passage?
A.
In a sense we may call the United States a 'bypass nation'.
B.
In Canada and the U.K. bypass operations are less performed because their medical levels are relatively lower.
C.
Bypass operations can solve the heart patients' problems once and for all.
D.
Recent study shows that nearly all of the bypass operations in the United States are proved useless and needless.