What does it mean to be as fragile as a house of cards?

Aeasily destroyed or spoilt (This igloo is as fragile as a house of cards; I want to leave before it collapses!)

Bvery soft (The cover of my new book is as soft as velvet)

Cvery soft or gentle (The singer's sweet voice sounded as soft as silk)

Dvery thin (This path is as thin as a rail)