Answer:
C. To the two legs of a compass.
Explanation:
John Donne's poem "A Valediction: Forbidding Mourning" is a metaphysical poem about the parting of two lovers. This farewell speech of the poet and his wife is a form of forbidding a person to be sad at the parting.
Lines 25 to 28 goes as follows-
<em>If they be two, they are two so </em>
<em> As stiff twin compasses are two; </em>
<em>Thy soul, the fixed foot, makes no show </em>
<em> To move, but doth, if the other do.</em>
It is here that the speaker makes a comparison between him and his lover and the two feet/ legs of a compass. Thus, the correct answer is option C.