Each foot consists of two unstressed syllables followed by a stressed syllable.
Each foot consists of one stressed syllable followed by one unstressed syllable.
Each foot consists of three consecutive stressed syllables.
Each foot consists of one unstressed followed by a stressed syllable.
The statement about iambic meter that is true is the last one - Each foot consists of one unstressed syllable followed by a stressed syllable. For example: Shall I compare thee to a summer's day.
