The answer is: d. thy firmness makes my circle just/and makes me end.
In the poem "A Valediction Forbidding Mourning," the author John Donne reflects on his own death and suggests he does not want his wife to mourn because their love goes beyond the physical world. Thus, he compares their love with a compass: his wife's firmness makes him draw a perfect circle - meaning that she makes him complete. As a result, if she is strong, he soon will be where he belongs.