How many iambs are found in this line “Rough winds do shake the darling buds of May”

Ten, because an iamb is a count of the individual syllables in a poetic line.

Explanation:

An iamb is a metrical foot of poetry where the short syllable is followed by a long syllable. In short, we can also say an iamb is a foot of two syllables, with an unstressed syllable followed by a stressed syllable.

In the given line "rough winds do shake the darling buds of May" is of ten iambs. This is because an iamb is a count of the individual syllable in a poetic line.

Thus, the correct answer is the fourth option.

some sort of sound device i believe.