The correctly written sentence is "At the moment Pierre is on a diet." The other sentences contain grammatical errors or awkward phrasing. For example, "From June Tony has been dieting" should specify a more complete timeframe, while "We have a porch on front of your house" is missing "the" before "front."
Pierre Chareau has written: 'Pierre Chareau'
Pierre Arnold has written: 'Pierre Arnold'
Pierre Caille has written: 'Pierre Caille'
Pierre Laval has written: 'The diary of Pierre Laval'
Pierre Pineau has written: '\\'
Pierre Soulages has written: 'Entretien avec pierre Soulages'
Pierre Dumont has written: 'Pierre Dumont, 1884-1936'
Pierre Boiron has written: 'Pierre Kast' -- subject(s): Criticism and interpretation, Pierre Kast
Pierre Pelloux has written: 'Pierre Pelloux' -- subject(s): Exhibitions
Pierre-Humbert. has written: 'Pierre-Humbert' -- subject(s): Exhibitions
Pierre Leclercq has written: 'Illusion'
Pierre Cottel has written: 'Wallers'