便利だ
The subway is convenient.
地下鉄が便利です
The subway is the most convenient.
地下鉄が一番便利です
The subway is the most convenient for getting to work.
出勤するとき地下鉄が一番便利です
The subway is the most convenient especially for getting to work.
特に出勤するとき地下鉄が一番便利です
The subway is the most convenient in the city, especially for getting to work.
都市では特に出勤するとき地下鉄が一番便利です