What is the main idea of the passage?
A.Tides are influenced more by Moon than by the Sun.
B.Tides are  a natural phenomenon but are not natural disaster .
C.Tides always occur over water and are usually predictable.
D.Tides are a phenomenon mainly caused by forces of gravity.

Mark the letter A, B, C or D to show the underlined part that needs correction.
Please arrive early so that we were able to start the meeting on time.
A.early
B.so that
C.were able
D.on time.

(45)..................
A.planning
B.preparing
C.practising
D.organising

(44).....................
A.insist
B.wait
C.ask
D.expect

(43)...................
A.native
B.resident
C.local
D.national

(42)....................
A.soon   
B.far      
C.well
D.long

(41) .....................
A.occupy
B.work
C.employ
D.staff

(40).......................
A.function
B.use
C.aim     
D.purpose

(39)..................
A.to
B.for
C.at
D.in

Why does the author mention tsunamis in the passage? 
A.To explain that not all tides are caused by gravity.
B.To give an example of an extreme tidal phenomenon.
C.C. To show that they are not related to natural tides.
D.To suggest that more categories for tides area needed.