Learning a foreign language calls for your memory,time,patience and emotions.________ it is not a simple thing.
On the top of the mountain __________.
The WHO thinks highly of the measures all the departments in China __________ to prevent large-scale outbreak of the disease.
__________ twice a year is the rule that every driver shall obey in this city.
Playing on the football pitch __________.
With the development of the Internet, e-mail has largely __________ the traditional business letter.