Naps--short sleeps during the day--may improve memory, experts said recently.  New research conducted by brain researcher Avi Karni of the University of Haifa in Israel explores the possibility that naps help lock in sometimes long-term memories. "We still don't know exactly how memory system works during sleep, but the results of this research suggest it is possible to speed up memory consolidation ," Karni said. Long-term memory refers  to memories that stay with us for years, such as "what" memories -- a car accident that happened yesterday-- or "how to" memories, such as one's learned ability to play the pianos. Karni, also one of the authors of the study published in a recent issue of the journal Nature Neuroscience, instructed participants to learn a difficult set of finger games, then divided the study _ into two groups: one that napped for an hour, and one that didn't. The people who took an afternoon snooze showed obvious improvement in their performance by that evening. "After a night's sleep the two groups were at the same level, but the group that slept in the afternoon improved much faster than the group that stayed awake," Karni said. And the study also showed just how much faster a 90-minute nap could help lock in long-term memories. "Daytime sleep can shorten the time 'how to' memory weakens and forgetting starts,"Karni said, "Instead of 6 to 8 hours, the brain consolidated the memory during the 90-minute nap." We can learn from the article that   _  .
the new research has discovered the memory process during the sleep taking a nap helps improve both long-term and short-term memories Karni's findings are based on comparisons between two groups of participants people who take a nap will never forget "how to" skills once they are learned
Question: Naps--short sleeps during the day--may improve memory, experts said recently.  New research conducted by brain researcher Avi Karni of the University of Haifa in Israel explores the possibility that naps help lock in sometimes long-term memories. "We still don't know exactly how memory system works during sleep, but the results of this research suggest it is possible to speed up memory consolidation ," Karni said. Long-term memory refers  to memories that stay with us for years, such as "what" memories -- a car accident that happened yesterday-- or "how to" memories, such as one's learned ability to play the pianos. Karni, also one of the authors of the study published in a recent issue of the journal Nature Neuroscience, instructed participants to learn a difficult set of finger games, then divided the study _ into two groups: one that napped for an hour, and one that didn't. The people who took an afternoon snooze showed obvious improvement in their performance by that evening. "After a night's sleep the two groups were at the same level, but the group that slept in the afternoon improved much faster than the group that stayed awake," Karni said. And the study also showed just how much faster a 90-minute nap could help lock in long-term memories. "Daytime sleep can shorten the time 'how to' memory weakens and forgetting starts,"Karni said, "Instead of 6 to 8 hours, the brain consolidated the memory during the 90-minute nap." We can learn from the article that   _  .
A. the new research has discovered the memory process during the sleep
B. taking a nap helps improve both long-term and short-term memories
C. Karni's findings are based on comparisons between two groups of participants
D. people who take a nap will never forget "how to" skills once they are learned
Answer: