建筑用的钢材在出厂之前都要经过发蓝处理,使其表面生成一层四氧化三铁,其目的是( )
The children loved their day trip, and they enjoyed the horse ride ______.
Progress______ so far very good and we are sure that the work will be finished on time.
Charles was alone at home, with_______ looking after him.
It is often ______ that human beings are naturally equipped to speak.
I can’t leave. She told me that I ______ stay here until she comes back.