💡 Detailed Explanation
The correct answer is 「反面」 (hanmen), meaning 'on the other hand' or 'while... on the contrary', expressing contrasting qualities of the same thing. 「一方」 (ippō) also means 'on the other hand' but is more neutral, while 「反面」 strongly emphasizes opposite, contrasting aspects of the same entity. 「つつも」 means 'although'. 「ものの」 means 'although/even though'.