Напишите уравнения следующих превращений: FeS →H2S →Na2s.

Помогите,пожалуйста,выберить правильный вариант ответа.

  Jeff and Celia are walking in/at the village. They often do this at/in  the weekend. They walk from their house against/to the park, and then they go back again. Today, it is very sunny. Jeff and Celia have stopped to look at the flowers. They are standing under/over the branches of a large tree. They have just walked above/across the small white bridge in/among the park. There is a wooden bench near/behind the flowers, which Celia likes to sit at/on when she gets tired.

становится ли массивнее железнодорожный рельс,когда он нагревается в жаркий солнечный день?почему?