Here's why:
* Onomatopoeia is the use of words that imitate the sounds they represent.
* In this sentence, "g" is meant to represent the sound of a plate hitting the ground.
Let's analyze the other sentences:
* "Happiness is sipping soda on a Saturday" - This sentence uses descriptive language but doesn't imitate any sound.
* "The green grass needed grazing" - This sentence describes a need but doesn't imitate any sound.
* "Have seat and give you treat" - This sentence uses everyday language and doesn't imitate any sound.