Xavier
The proper noun is Jessica, the name of a person. A proper noun always starts with a capital letter.
Some proper nouns that begin with G are:GabonGambia, TheGeorgiaGermanyGhanaGreeceGrenadaGuatemalaGuineaGuinea-BissauGuyanaGatoradeGeorge GershwinGlamour MagazineGolden Gate BridgeGone With the WindGoodyear TiresGrand CanyonGrand Rapids, MichiganGreat Barrier ReefGreyhound LinesGuthrie, Woody and Arlo
Nope. Common noun.
David's
Yes
Some proper nouns that start with the letter G:GameStop CorporationGeorgiaGermanyGertrude SteinGiorgio ArmaniGlenda the Good WitchGolden Gate BridgeGone With the Wind (1939)Grand Canyon (The)GREGORY
NO!!! 'Janet' is a proper noun. It is a female forename. derived from the male 'John'. Being a proper noun it starts with a capital letter.
X-ray
xanadu
Proper nouns.
Yes, "Stefan" is a proper noun because it is a specific name for a person, place, or thing. It always starts with a capital letter.