已知曲线y=$\frac{x^2}{4}$-3lnx的一条切线的斜率为$\frac{1}{2}$，则切点的横坐标为(     )

    On Tuesday, scientists announced that they have discovered the bones of four settlers in Jamestown, Virginia. Jamestown was the first permanent English settlement in what become the United States. The bones were unearthed under the floor of a Jamestown church which was discovered in 2010 and is considered as America‘s first Protestant church.

    The Jamestown Rediscovery Foundation at Historic Jamestowne and the Smithsonian's Museum of Natural History announced that the settlers held high leadership positions. The men, Rev.Robert Hunt,Capt. Gabriel Archer,Sir Ferdinando Wainman,and Capt. William West, all played a role in the Jamestown settlement. After being lost to history for more than 400 years, the discovery of their remains provides new clues about their life and the importance of religion in the 1600s.

    “This is a very important discovery,” Jamestown Rediscovery Foundation President James Horn said in a statement. “These men were among the first founders of English America."

    About 100 people settled along the James River in what would become the first English settlement m 1607. During that time, settlers in Jamestown were faced with famine and disease The colony was nearly wiped out due to conflict with Native Americans in the area and with other English settlers.

    "They lived and died at a hard time in the history of the settlement , when Jamestown almost ended in  failure," Horn said. “The bones of these men help fill in the stories of their lives ”

    The Smithsonian and the Rediscovery Foundation found the remains in November of 2013. Scientists used 3-D technology to locate the exact gravesites of the men. The team wanted to identify its findings before announcing the discovery. They identified the men using historical records and studied the chemicals of the bones to learn what the men ate and where they came from.

    Findings from the burials will go on display within weeks at Historic Jamestowne. The site also plans to honor the men and will keep their bones in a safe place for future study.

王安石在《感事》一诗中写道：“贱子昔在野，心哀此黔首(百姓)。丰年不饱食，水旱尚何有？”为解决以上问题，他变法时采取的措施有
①青苗法　②募役法　③农田水利法　④方田均税法

    Dolphins (海豚) live in a dark underwater world. It's often impossible to see each other or anything else around them, so sound plays an important role in their survival. To communicate with each other, dolphins produce all kinds of sounds.

    Only other dolphins understand what the sounds mean. Scientists haven't uncovered their secret communication, except for one kind of whistle. It might last less than a second, but this whistle is a big deal. Why? Because these whistles are actually names of dolphins — and every dolphin has one. Scientists call these sounds a “signature whistle.” When other dolphins hear the whistle, they know which dolphin is calling.

    Dolphins often hunt by themselves but still need to stay connected to the group. Since they can't always see each other, dolphins use their signature whistles to check in with other dolphins hundreds of yards away. “In coastal areas, dolphins exchange whistles even when they're a third of a mile apart,” says Greg Campbell, who studies animals. That means dolphins shout out to group members that might be nearly five football fields away.

    What's amazing is who names the baby dolphin. Not the mother. Not an auntie dolphin or another group member. Scientists believe the baby dolphin itself comes up with the signature whistle. Like human babies, a baby dolphin plays with sounds throughout its first year. While testing its sound skills, a baby dolphin is doing something amazing. It's creating or figuring out its signature whistle. How or why it chooses its signature whistle is not clear. Studies show that most of the time the signature whistle is nothing like its mother's or group members' whistles.

    When the baby dolphin is about a year old, its signature whistle is set. It repeats it often so the other dolphins learn to recognize it.

    Deciphering(破译) dolphin names is just the beginning of figuring out what dolphins communicate about. Do they chat about sharks? Discuss the tides? Maybe they even have a name for people. Someday scientists are to decipher the rest of dolphins' communication.