(C)   According to some studies, counting is not an inborn ability but an   23     one. In fact, it took human beings thousands of years   24   how to count with numbers. Before complicated counting systems were developed, people   25     things through a tallying system. If shepherd had twenty sheep, he would     26     twenty stones. Around 3500 BC,   27    numbers were invented in Mesopotamia because Mesopotamians began to   28   in commercial activities. These numbers made counting much faster because they always kept the same value. After Mesopotamia’s pioneering achievement, each civilization also developed its own number system. Egyptian numbers were made up of little pictures, such as   29     of frogs and lotus flowers. Roman numbers like I, V, X, etc., can still be found on some official   30    . We all   31    numbers every day in countless numbers of ways. We should be grateful that now we don’t need stones to count our sheep.
【題組】23
(A)inquired
(B) complicated
(C)acquired
(D) required