💡 Detailed Explanation
The adjective 'きつい' (kitsui) is used to describe work that is physically or mentally demanding, exhausting, or tough. Therefore, its meaning aligns with '大変な' (taihen na), which means 'hard', 'challenging', or 'difficult'. The other options refer to different qualities: '退屈な' means boring, '簡単な' means easy, and '危険な' means dangerous.