有四位学生进行如下操作：甲将反光镜对着太阳光以便视野内达到最大亮度；乙观察头发时，两眼张开，左眼观察，右手画图；丙发现目镜脏了，于是拿起卫生纸擦干净；丁使用低倍物镜已看到细胞，仍觉得有些模糊，于是试着调细准焦螺旋。其中正确的操作是 [ ]

A．甲、乙、丙

B．乙、丁

C．甲、乙

D．乙、丙

–I tried many times, but I still failed in the experiment.

--Don’t be discouraged. _______ and the problem will be settled.

A．Having a little effort

B．There is a little effort

C．If you have a bit effort

D．A bit more effort