# 單元測試三 <quiz> <question> <p>1.[單選](2分)啟動ROS Master的命令是：</p> <answer correct>A.roscore</answer> <answer>B.rosmaster</answer> <answer>C.rosMaster</answer> <answer>D.roslaunch</answer> <explanation>你選對了</explanation> </question> </quiz> <quiz> <question> <p>2.[單選](2分)關于ROS Node的描述，哪一項是錯誤的?</p> <answer>A.Node啟時會向Ｍaster注冊</answer> <answer correct>B.Node可以先于ROS Master啟動</answer> <answer>C.Node是ROS可執行文件運行的實例</answer> <answer>D.Node是ROS的進程</answer> <explanation>你選對了</explanation> </question> </quiz> <quiz> <question> <p>3.[單選](2分)關于.launch文件的描述，以下哪一項是錯的?</p> <answer>A.可以加載配置好的參數，方便快捷</answer> <answer>B.通過roslaunch命令來啟動launch文件</answer> <answer correct>C.在roslaunch前必須先roscore</answer> <answer>D.可以一次性啟動多個節點，減少操作</answer> <explanation>你選對了</explanation> </question> </quiz> <quiz> <question> <p>4.[單選](2分)想要查看`/odom`話題發布的內容，應該用哪個命令?</p> <answer correct>A.rostopic echo /odom</answer> <answer>B.rostopic content /odom</answer> <answer>C.rostopic info /odom</answer> <answer>D.rostopic print /odom</answer> <explanation>你選對了</explanation> </question> </quiz> <quiz> <question> <p>5.[單選](2分)請練習rosmsg命令，下列哪個不是std_msgs下的消息?</p> <answer correct>A.std_msgs/LaserScan</answer> <answer>B.std_msgs/Header</answer> <answer>C.std_msgs/Time</answer> <answer>D.std_msgs/Float32</answer> <explanation>你選對了,LaserScan在sensor_msgs功能包下</explanation> </question> </quiz> <quiz> <question multiple> <p>6.[多選](5分)關于Topic通信的描述，正確的選項有：</p> <answer correct>A.Topic是一種異步通信機制</answer> <answer>B.一個Topic至少要有一個發布者和一個接收者</answer> <answer correct>C.查看當前活躍的Topic可以通過rostopic list命令</answer> <answer>D.一個Node最多只能發布一個Topic</answer> <explanation> B、錯誤。一個Topic可以被發布而無人接收，也可以一直被接收而無人發布。 D、錯誤。一個Node可以發布多個Topic，例如仿真示例中的/gazebo節點。</explanation> </question> </quiz> <quiz> <question> <p>7.[判斷](2分)同一個Topic上可以有多個發布者.</p> <answer correct>A.正確</answer> <answer>B.錯誤</answer> <explanation>一個Topic上可以有多個發布者，例如/tf, /rosout</explanation> </question> </quiz>