What is an iamb?
a. an unstressed syllable followed by a stressed syllable
b. a type of poem dealing with rural settings
c. a line of poetry in which there are five stressed syllables
d. a line of unrhymed verse

A. An unstressed syllable followed by a stressed syllable

Explanation:

In poetry, an iamb is a metrical foot (a group of syllables) that has one UNSTRESSED syllable followed by a STRESSED syllable. For example, the word remark is an example of an iamb because re is an unstressed syllable and mark is a stressed syllable.

Lines of poetry can contain different types of iambs depending on the number of iambs that there are per line. These types are dimeter (two iambs per line), trimester (three iambs), tetrameter (four iambs), pentameter (five iambs) or hexameter (six iambs).

b would have to be the answer