A pentameter is a line in verse consisting of five metrical feet.
Iambic pentameter is one of the most commonly used meters in English poetry. It is a metrical foot in poetry that refers to the number of syllables in a line and the emphasis placed on them. According to this pentameter, an unstressed syllable is followed by a stressed syllable.
According to this, the line that uses iambic pentameter is option A "Is Martin Lewis going mad, my dear?" because it presents an unstressed syllable followed by a stressed one.
