17．The world's population has reached 7billion（十億）according to the United Nations（聯(lián)合國）by 2011．It comes just 12years since the total reached 6billion-with official estimates saying the population will top 8billion in 2025 and 10 billion before the end of the century．
And it is most likely that the 10-billionth baby will be born in the Asia-Pacific region-where the population growth rate is higher than anywhere else in the world．
Of the 2.3billion people，the United Nations believes will be added by 2050，more than 1billion will live in sub-Saharan Africa．The Indian subcontinent（次大陸）will add some 630million people．
With more people to feed，more houses & medical care to provide，experts say the world's resources（資源）will face more strain than before．
52．According to the picture，the population of the world reached 6billion inB．
A.1987
B.1999
C.2011
53．We know that more than 1billion will live inA by 2050．
A．sub-Saharan Africa
B．Indian subcontinent
C．the United States
54．According to the picture，B will have the largest population in 2050．
A．China
B．India
C．Nigeria
55．The underlined word"strain"in the last paragraph（段落）means"C"．
A．破壞
B．關(guān)閉
C．壓力
56．The population of the world growsB according to the picture．
A．slower and slower
B．faster and faster
C．smaller and smaller．
