Option 1 -> This relates to company profits, not the direct harm suffered by labourers themselves.
Option 2 -> While being called "coolies" was derogatory, this alone doesn't capture the systemic harm described in the passage.
Option 3 -> The passage explicitly states labourers "endured harsh working conditions and were subjected to exploitative practices" and the system "perpetuated social and economic inequalities."
Option 4 -> Training in cultivation methods is not mentioned as a problem, and lack of training doesn't represent the core detriment described.
Hence, Option 3 -> The passage clearly identifies that indentured labourers faced exploitative practices, harsh working conditions, and the system perpetuated social and economic inequalities, making this the most comprehensive answer about how the system was detrimental to plantation labourers -> correct