要利用凸透镜使小灯泡发出的光变成平行光，应该把小灯泡放在凸透镜的焦点上，这里利用了 ____ 的原理．
折射时光路是可逆
Hearing his father was seriously ill, ______.
A．he burst into tears
B．his eyes were filled with tears
C．his face lost its colour
D．tears came to his eyes
高甘油脂血症病人应用后可使LDL-C升高的是（）。
A.苯扎贝特
B.氯苯丁酯
C.吉非贝齐
D.环丙贝特
E.非诺贝特
