某班同学在用光学显微镜观察装片时，由于突然停电导致视野偏暗．在如下所采取的措施中，较为合理的是（　　）

A．将凹面镜转换成平面镜

B．使用遮光器上的更大光圈

C．调节粗准焦螺旋

D．调节细准焦螺旋

Our English teacher devoted herself _____ to her teaching and it earned her a good reputation in our school.[ ]

A. strongly

B. extremely

C. entirely

D. freely