Don’t make a noise! They on a physics problem now.
A. will work
B. are working
C. worked
D. have worked
网友回答
A. will work
(答案→)B. are working
C. worked
D. have worked
解析：此题考查现在进行时的基本用法。表示正在进行的动作。句意：不好出生。他们现在正在解决一道物理问题。结合语境及时间状语，可知下文描述的是现在正在进行的动作，故用现在进行时态。选B。