`1.` Her mother told her that she had to finish her work before bedtime

`-` S + told/ said to + O + (that) + S + V_lùi thì

`-` Lùi thì: must `→` had to

`2.` Nancy has not come here since 1990

`-` S + has/ have + (not) + V_ed/ V3 + since + mốc thời gian

`3.` We used to light our houses with candles

`-` S + used to + V_inf: Đã thường làm gì nhưng giờ không còn làm nữa

`4.` It's very dangerous to play with matches

`-` It's + adj + to + V_inf: Thật là như thế nào để làm gì

1. Her mother said she had to finish her work before bedtime.
2.Nancy hasn't come here since 1990.
3.we used to lit our houses with candles.
4.it is dangerous to play with matches.