Close relationships, thought to help communication by giving speakers a common context, are actually more likely to make  _ when strangers are involved, a new study suggests. Because close colleagues and friends already share so much common knowledge that they often use short, ambiguous  messages which can lead to misunderstandings. "People are so used to talking with those with whom they already share a great deal of information that, when they have something really new to share, they often present it in a way that they assume the person already knows it." says study-team member Boaz Keysar. Keysar and his graduate student, Shall Wu, trained 40 pairs of undergraduate students to memorize made-up names and descriptions of strange shapes. In each pair, the "director" had to communicate the identity of one of the 24 shapes. The partner had to use the information to choose the correct shape from a set of three images on a computer monitor. Half of the partners studied only the first six shapes, while the others learned the first 18 shapes. The directors, who had memorized all the shapes, were aware of their partners' knowledge levels of the shapes. In the pairs with the most shared knowledge, the directors were more likely to rattle off  shape names, compared with pairs with little knowledge overlap , in which the directors were more likely to describe the actual shapes. Not surprisingly, participants with more shared knowledge were twice as likely to ask for clarification as those with less overlap. Language itself can be confusing. "The reason all this is happening at all is that language in general is ambiguous," said Keysar. He recalls an ambiguous billboard near a stadium holding a Rolling Stones concert that night. The billboard read, "Avoid LSD tonight." (:LSD"") Hmmm? "It was about Lake Shore Drive, and I'm sure the writer of the sign didn't realize he was being ambiguous," Keysar said. "Even though miscommunication can lead to missed meetings or deadlines, people are often unaware when their language is ambiguous," Keysar added, "We don't realize we say things that are ambiguous," he said, "and that's a problem." It can be inferred from the example of the billboard that   _  .
most people know what LSD usually refers to local people would not misunderstand the meaning of LSD the writer of the sign means to play jokes on those attending the concert people sometimes ignore the limitation of shared knowledge
Question: Close relationships, thought to help communication by giving speakers a common context, are actually more likely to make  _ when strangers are involved, a new study suggests. Because close colleagues and friends already share so much common knowledge that they often use short, ambiguous  messages which can lead to misunderstandings. "People are so used to talking with those with whom they already share a great deal of information that, when they have something really new to share, they often present it in a way that they assume the person already knows it." says study-team member Boaz Keysar. Keysar and his graduate student, Shall Wu, trained 40 pairs of undergraduate students to memorize made-up names and descriptions of strange shapes. In each pair, the "director" had to communicate the identity of one of the 24 shapes. The partner had to use the information to choose the correct shape from a set of three images on a computer monitor. Half of the partners studied only the first six shapes, while the others learned the first 18 shapes. The directors, who had memorized all the shapes, were aware of their partners' knowledge levels of the shapes. In the pairs with the most shared knowledge, the directors were more likely to rattle off  shape names, compared with pairs with little knowledge overlap , in which the directors were more likely to describe the actual shapes. Not surprisingly, participants with more shared knowledge were twice as likely to ask for clarification as those with less overlap. Language itself can be confusing. "The reason all this is happening at all is that language in general is ambiguous," said Keysar. He recalls an ambiguous billboard near a stadium holding a Rolling Stones concert that night. The billboard read, "Avoid LSD tonight." (:LSD"") Hmmm? "It was about Lake Shore Drive, and I'm sure the writer of the sign didn't realize he was being ambiguous," Keysar said. "Even though miscommunication can lead to missed meetings or deadlines, people are often unaware when their language is ambiguous," Keysar added, "We don't realize we say things that are ambiguous," he said, "and that's a problem." It can be inferred from the example of the billboard that   _  .
A. most people know what LSD usually refers to
B. local people would not misunderstand the meaning of LSD
C. the writer of the sign means to play jokes on those attending the concert
D. people sometimes ignore the limitation of shared knowledge
Answer: