Hfe, the current amplification factor (also called β), is an intrinsic parameter of each bipolar transistor. Which of the following statements is correct?

A、The current amplification factor of the transistor is a constant.;
B、The Hfe of each transistor is different and it varies slightly with temperature and current.;
C、Hfe is the measured value in the saturated state of a transistor.;
D、Hfe = Ic/ Ib