阅读下面短文，请从短文后所给各题的4个选项(A、B、C、D)中选出一个最佳选项。

     It is a cold March evening on a farm in South England. Outside, 2000 sheep are standing in the fields. Most of them will give birth to lambs in the following weeks. Inside, their shepherds（牧羊人） are sitting in the warm watching TV.
     You might think that the shepherds are neglecting their duty by resting in comfort. However, if you look at the television more closely, you would see that the shepherds are protecting the sheep.
     It is part of an experiment to try to increase the survival rate of new lambs. In the past, the shepherds stayed out with their sheep, walking round and helping the mother sheep to give birth. In this experiment, television cameras are used to scan the sheep, and the shepherds are looking at a television monitor which is automatically controlled.
     The system has several advantages. Shepherds do not have to walk among the sheep, which tends to disturb the mother sheep that are about to give birth. Instead, they can stay inside, watching by remote control. If there is no problem, they stay away from the sheep. But when they are needed they can quickly go out to help, or to scare away foxes. The experiment is popular with shepherds because it means that they do not have to spend all their time outdoors waiting for the lambs to arrive in freezing weather.
     The monitoring system is rented for the few months when the lambs are born. The cost is high, but the farm manager estimates that, since lambs are so valuable, and if about ten more lambs are saved than in a usual year, the experiment will be financially worthwhile. At the same time, the experiment may show that it is possible to make a saving in manpower, especially when a large number of sheep are involved.