www thuvienhoclieu com Unit 12 AN OVERCROWDED WORLD ( PART 1 GRAMMAR REVIEW ) 1 Comparisons of quantifiers more, less/ fewer more + traffic/ pollution/ food/ problems/ solutions than less + nutrition/ clean water than fewer + diseases/ criminals than 2 Tag questions A tag question is a short question It follows statement It’s added at the end, after a comma Examples Overpopulation is a serious problem, isn’t it? Traffic jam is the most serious problem, isn’t it? Note A positive sentence ha[.]