It fits to an appropriate temperature when subjected to low-temperature tempering of the following? ① 550 ~ 600 ℃ ② 350 ~ 400 ℃ ③ ℃ 250 ~ 300 ④ 150 ~ 200 ℃
the task of the low temperature; when the temperature is appropriate, as it is.① 550 or 600 degrees② 350 or 400 degrees③ 250 or 300 degrees④ 150 or 200 degrees