1. A 热 (rè) in Chinese means “hot” or “passionate.” 热恋 (rèliàn) means “to be deeply in love” with somebody. B is 初恋 (chūliàn) and C is 失恋(shīliàn)
2. C 他是我的初恋。(Tā shì wǒ de chūliàn.) Here, 初恋 (chūliàn) is describing a person, not a first love affair.
3. C C is used when people comfort those who are lovelorn.