请教prep2-143

143 Although
        the
        vast
        constellation
        of
        small
        islands
        that
        dot
        the
        South
        Pacific
            has
        a
        population
            of
            only
        a

few
        million
            people,
                it
        is
        home
        to
        about
            a
            sixth
            of
            the
            world's
            6,000
            or
            so
            languages.

(A)
            Pacific
            has
            a
            population
            of
            only
            a
            few
                million
            people,
            it
            is

(B)
            Pacific
            has
            a
            population
            of
            only
            a
            few
                million
            people,
            they
            are

(C)
            Pacific
            is
            populated
            by
            a
            only
            a
            few
            million
            people,
            and
            it
            is

(D)
            Pacific,
            having
            a
            population
            of
            only
            a
            few
            million
            people,
            is
            nonetheless

(E)
            Pacific,
                populated
            by
            only
            a
            few
            million
            people,
            yet
            they
            are

答案是A  我不明白的是C有什么问题？prep给的解释是：
        连词and多余，这样使得句子缺少主句结构。我不是很明白这个解释，请给为帮忙