The old woman spoke to the girl again，raising his voice a bit，but still no answer.
A．received B．receiving C. had received D to receive
_________ made him worried.
A．Not known how to do it B．Unknown what to do
C．Our Knowing not how to do D．Our not knowing how to do it
To succeed in a difficult task,______________.
A) Persistence is needed B) Persistence is what you need
C ) One needs to be persistent D ) A persistent nature is needed