[单选题]Which of the following statements of vacuum tube is NOT true? ( )eK1答案窝(daanwo.com)-大学生作业答案及考资分享平台
A It had an internal power heater.eK1答案窝(daanwo.com)-大学生作业答案及考资分享平台
B Its life can reach millions of hours.eK1答案窝(daanwo.com)-大学生作业答案及考资分享平台
C It is bulky.eK1答案窝(daanwo.com)-大学生作业答案及考资分享平台
D It gave off heat.eK1答案窝(daanwo.com)-大学生作业答案及考资分享平台
eK1答案窝(daanwo.com)-大学生作业答案及考资分享平台