题干

下列调查活动或实验中,计算所得数值与实际数值相比,可能偏小的是(   )

A:标志重捕法调查野兔种群密度时个别标志物脱落

B:调查某遗传病的发病率时以患者家系为调查对象

C:样方法调查法国梧桐种群密度时在分布较稀疏的地区取样

D:用血球计数板计数酵母菌数量时统计方格内和在相邻两边及其顶角的菌体

上一题 下一题 0.0难度 选择题 更新时间:2012-03-11 10:44:57

答案(点此获取答案解析)

C

同类题2

   The teacher stood before his class and was going to hand out the final exam papers. “I know how  1   you have all worked to prepare for this test,” he said. “And because I know you can do it well, I am willing to offer a B to anyone who would  2  not to take the test. ”
   Many students jumped up to   3   the teacher and left the classroom.  The teacher looked at the   4  students and said, “Does anyone else want to get a B? This is your last   5 . ” Two more students decided to go.     Seven students remained.  The teacher then handed out the  6   .  There were only three sentences typed on the paper: Congratulations! You have just   7   an A in this class.  Keep believing in yourself.     I never had a teacher like that, but I think it is a test  8   any teacher could and should give.  Students who are not   9   in what they have learned are B students at best(充其量). The same is   10   in real life.  The A students are those who believe in what they are doing because they have   11   both successes and failures.  They have learned life’s lessons, either from normal education   12  from events in their lives, and have become   13   people.      Scientists say that by the age of eight, 80% of what we believe about ourselves has already been formed.  You are a big kid now, and you   14   that  you have some limits (限制).  However, there is   15   you can’t do or learn or be.  Sir Edmund Hillary, the first person to reach the summit of Mount Everest said, “It’s not the mountain we conquer(克服) but ourselves. ”