Iambic tetrameter?

Iambic= metrical foot used in poetry.

It simply refers to the flow of poetry where an iamb describes when syllabic verse is accentuated. In this case an iambic foot=unstressed syllable (pronounced with no emphasis) followed by a stressed one (pronounced with emphasis).

Iambic tetrameter= 4 iambic feet so= 4 pairs of unstressed then stressed.

Answer= Lines1 and 3

A easy way of figuring this out is to note how lines 1 and 3 have 8 syllables and 2 and 4 have 6. Also you would also recite lines 1 and 3 with an iambic tetrameter with unstressed and stressed emphasis.