在一般疑问句前加特殊疑问词。
(当特殊疑问词为主语时，除外)
例1：
Lily is
watching TV
now.
例1：
What
is Lily doing now? （疑问词 what+一般疑问句 is Lily doing now?）
例2：
Lily
is watching TV now.
例2：
Who
is watching TV now? （疑问词 who 做主语，整个句子为主系表结构。）