There are no buses, ________ you’ll have to walk.
Their school days are busy and the children don’t get home _____7 o’clock p.m.
The little girl likes to _______ as an angel(天使), so she asks her mother to buy her lots of clothes.
We all know trees play an important role in _______up the air.
Lucy and Lily are twins, but they are different _____each other in many ways.
It is necessary for students ______ good studying habits.