题目

阅读短文，根据意思，从各题所给的A、B和C三个选项中选出最佳答案。并在答题卡上将该编号字母涂黑。 Most teenagers feel sad or afraid when their parents fight. They might think their parents don’t love each other any more. In fact, it is normal for parents to disagree and argue sometimes. They might disagree about important thing like jobs and family decisions. They might even disagree about little thing that don’t seem important at all – like what’s for dinner. Maybe sometimes parents feel so strongly about their differences that it may le如何测量一棵大树的树干直径？（写出所需器材及实验步骤和相应表达式）