Now I can hear Lily in the classroom. A. sing B. singing C. sings

问题补充：

Now I can hear Lily in the classroom.

A. sing B. singing C. sings

答案：

解析：有now 表示现在正在发生，根据hear sb do sth或doing sth，前者表示已经做过，而后者某人正在做，故选B