Many firms give away small quantities of their productions as _______ so that people can try them before buying.

Whether by accident or  _____  , he arrived too late to help us.

 What on earth did you tell her? The __________ on her face suggested that she was more than angry.

. —Li Hua was in London for two years.   —It’s no ___ he can speak English so well.

They put_______on the government to lower taxes and give laid-off workers necessary health care.