Causing strong disagreement because people hold very different opinions about it.
“The city council's decision to ban plastic bags has become a controversial topic among residents.”
“Remote work policies remain controversial, with employees and employers holding opposing views.”
Reading Part 4 is always built around a controversial issue, so this idea appears in almost every introduction. Recognizing it early tells you two opposing viewpoints are coming, letting you set up a mental 'side A vs. side B' map before reading the details.
Synonyms: contentious, divisive, disputed