下图表示某种兔迁入新的环境后种群增长速率随时间的变化曲线。第3年时用标志重捕法调查该兔的种群密度，第一次捕获了50只全部标记后释放，一个月后进行第二次捕捉，捕获的兔中未标记的有60只，标记的有20只。该兔种群在该环境中的K值约是：

阅读下面诗歌，回答（1）～（4）题。

麂子

牛汉

                                                                                                                       远远的

                                                                                                                       远远的

                                                                                                                       一只棕红色的麂子

                                                                                                                       在望不到边的

                                                                                                                       金黄的麦海里

                                                                                                                       一蹿一蹿地似飞似飘

                                                                                                                       朝这里奔跑

                                                                                                                       四面八方的人

                                                                                                                       都看见了你

                                                                                                                       用惊喜的目光

                                                                                                                       用赞叹的目光

                                                                                                                       用担忧的目光

                                                                                                                       麂子

                                                                                                                       远方来的麂子

                                                                                                                       你为什么生得这么灵巧美丽

                                                                                                                       你为什么这么天真无邪

                                                                                                                       你为什么莽撞地离开高高的山林

                                                                                                                        五六个猎人

                                                                                                                        正伏在草丛里

                                                                                                                        正伏在山丘上

                                                                                                                        枪口全对着你

                                                                                                                        哦，麂子

                                                                                                                        不要朝这里奔跑

小王是个活泼可爱孩子，进入中学后，学习科目 增多了，忙乱极了。上课时，经常自个儿摸这摸那，老师讲到那儿都不知道。晚上在家复习功课时，心理总是在惦记着电视里的精彩节目。做作业时，一遇到难题 ，就马上去问别人。遇到那科要考试，才匆忙把课本拿起来翻这页看看，翻那页看看，忙到晚上十一点多，也理不出头绪来。因而，学习成绩总是不太理想。小王也知道这样不好， 但就不知道该怎么办呢？”
请你结合材料，运用所学知识，回答下列问题：