Answer:
The correct answer is 2. Five, because an iamb is an unstressed syllable and a stressed syllable.
Step-by-step explanation:
An iamb is a metrical foot which consists of two syllables: the first one is unstressed, and the second one is stressed. If you count the syllables in this line, you will see that there are 10 syllables in total. Divide this by two (because an iamb consists of two syllables), and you will see that there are 5 iambs in total.
Therefore, options 3 and 4 are incorrect. Option 1 is also incorrect because an iamb, as I already said, consists of two, not one syllable.