The correct option is D Tuscany is becoming everyone's favourite stop
The word 'hot' here describes the place, Tuscany, as a destination. In the context of the sentence, 'hot' means 'currently popular', 'in demand'. It does not literally mean hot: very high in temperature.
Option D gives the correct interpretation of the quoted speech, that Tuscany has suddenly become a popular destination. Hence D is the most suitable option.
Option A: This does not state the accurate meaning. It is not the main topic of discussion these days. But, Tuscany is a destination in demand these days. The meanings are different. Hence A is incorrect.
Options B and C give the literal meaning of hot, in terms of temperature. But Tina does not refer to the weather, but the nature of the destination, which is hot (popular, cool).
Hence B and C are incorrect.