— Excuse me, I want to have a letter mailed, but I can't find a post office.   

—  I know ______ nearby. Come on, I'll show you. [      ]

A. it          

B. one          

C. that        

D. another  

When action to avoid a close quarter situation is taken,a course change alone may be the most effective action provide that（）.

A.it is done in a succession of small course changes

B.It is not done too early

C.It is a large course change

D.the course change is to starboard