Base your answer to question 46 on the passage
below and on your knowledge of social studies.
…The deposits of fine sediment left by natural
floods sustain the fertility of floodplain soils. The
5,000-year history of agriculture in the Nile Valley
and delta of Egypt depended on the annual Nile
River flood that left a veneer of new silt over the
valley floor each year. Modern dams on the Nile
— particularly the Aswan High Dam, which can
store the entire annual flood — have destroyed
the natural system of fertilization, necessitating
huge imports of artificial fertilizers.…
— Oberlander and Muller, Essentials of Physical Geography
Today, Second Edition, Random House, 1987
Based on this passage, a valid conclusion would
be that
(1) natural fertilizers are less effective than
artificial fertilizers
(2) technological advances sometimes create
unforeseen problems
(3) yearly flooding is harmful to Egyptian
agriculture
(4) farmers in the Nile Valley operate at a
subsistence level