【单选题】A 72-year-old woman dies of congestive heart failure. The aortic valve is examined at autopsy (shown in the image). Which of the following is the most likely cause of aortic stenosis in this patient?
【简答题】It is sometimes said that strange flying objects have been seen high up in the sky. People call these strange objects Unidentified Flying Objects (UFO). These UFOs caused a lot of interest. Some of th...