If this be error and upon me proved, I never writ, nor no man ever loved.

These lines are an example of a/an
a. quatrain
b. octet
c. couplet
d. sestet

If it is originally written in two lines, it's a couplet.

quatrain = 4 lines together
octet = 8 lines together
couplet = 2 lines together
sestet = 6 lines together

These lines are an example of a couplet.

To determine the answer, we can break down the options:

a. A quatrain consists of four lines, while the given lines consist of only two lines.

b. An octet consists of eight lines, which is also different from the given lines.

c. A couplet is a two-line stanza or a pair of lines that often rhyme and have a distinct meaning on their own. The given lines exactly fit this description.

d. A sestet, on the other hand, consists of six lines, and the given lines do not meet this criteria.

Based on this analysis, we can conclude that the correct answer is c. couplet.