问题
选择题
People sell their products ____advertisement in the newspaper.
A．by putting an
B．to put an
C．by putting a
D．putting an
答案
答案：A
考查：介词by + doing 通过某种方式，advertisement 广告，它的发音以元音因素开头，所以一条广告用an advertisement，句意：人们卖产品通过在报纸上登广告的形式。所以选A。