题目洛氏硬度试验施加初试验力____，持荷()秒.A. ≤3B. ≤10C. ≤2D. ≤5洛氏硬度试验施加初试验力____，持荷()秒.A. ≤3B. ≤10C. ≤2D. ≤5题目解答答案A. ≤3