34. The word "untenable" (Line 3) in the last paragraph of the passage most probably means _____.

　　A) invaluable C) changeable

　　B) imaginable D) indefensible

　　35. Most philosophers believed that human nature _____.

　　A) is the quality distinguishing man from other animals

　　B) consists of competitiveness and selfishness

　　C) is something partly innate and partly acquired

　　D) consists of rationality and undesirable behavior

　　Passage Four

　　Questions 36 to 40 are based on the following passage.

　　Richard Satava, program manager for advanced medical technologies, has been a driving force in bringing virtual reality to medicine, where computers create a "virtual" or simulated environment for surgeons and other medical practitioners (從業者).

　　"With virtual reality we'll be able to put a surgeon in every trench," said Satava. He envisaged a time when soldiers who are wounded fighting overseas are put in mobile surgical units equipped with computers.

　　The computers would transmit images of the soldiers to surgeons back in the U.S. The surgeons would look at the soldier through virtual reality helmets (頭盔) that contain a small screen displaying the image of the wound. The doctors would guide robotic instruments in the battlefield mobile surgical unit that operate on the soldier.

　　Although Satava's vision may be years away from standard operating procedure, scientists are progressing toward virtual reality surgery. Engineers at an international organization in California are developing a tele-operating device. As surgeons watch a three-dimensional image of the surgery, they move instruments that are connected to a computer, which passes their movements to robotic instruments that perform the surgery. The computer provides, feedback to the surgeon on force, textures, and sound.