It was never clear _____ the man hadn't reported the accident sooner.
—He failed in the exam again.—He __________his teacher’s advice.
When first to the market, these products enjoy great success.
Armed with the information you have gathered, you can ___ preparing your business plan.
Cleaning women in big cities usually get by the hour.
Hearing the boring news, I was too distracted (心烦意乱)to my attention on my homework.