赞同English Expert老师对答案选C的认同。这道题,我估计是国人自己编的，不是考语法，是考事实，犹如脑筋急转弯。我在网上也查到了这道题。
    但对D答案，我和English Expert看法不同。如果撇开事实，D选项没有错。很多语法书都有讲解：one half /a half / half of the surface ... 以及half the surface的用法都是对的。一般one half 多用正式文体，或表示强调。a half 多用与口语。half the...  多见于美国英语，half of the ...多见于英国英语。
例句：
A half of the voters have not made up their minds.
Only half the guests had arrived by seven o'clock.
One half of the Moon appears to be illuminated by direct sunlight.
    另外，《朗文高级语法》第五章解释 Half of the...=half the...的例句： Half the country was against it.  Half of the country was against it.