In what sense is Petrarch insincere in Sonnet 18 (sonnet inside)?
a. Through professing his desire to be alone, he really craves the attention of other people.
b. While asserting he wants to keep his love a secret, he nevertheless tells many friends about it.
c. While failing to describe his lover's beauty, he still manages to flatter her.
d. Despite denying the power of his own poetry, he actually praises himself in the last lines.
The correct answer is C. The interpretation of the sonnet is as follows:
Lines 1–2: The poet declares he is ashamed that he has not yet written a poem about the lady's beauty.
Lines 3–8: The poet explains that the reason he has not written a poem about the lady's beauty is that he is not skillful or talented enough to create a poem that would do justice to her beauty, so he has not made the attempt.
Lines 9–14: The poet describes trying to write a poem about the lady's beauty but stopping before completing the work because the theme proved too high to be captured in verse.
The sonnet is obviously ironic. The poet is saying that the lady's beauty is so great that it demands a poem as a tribute, but that because her beauty is so great, no poem can be written that would do it justice. Nevertheless, this poem about not being able to write such a poem becomes the poem he says he has been unable to write. The question asks about insincerity. One might consider his words insincere, but they are better understood as playfully ironic. Either way, choice C is true. The poet never describes the lady's beauty in the poem, but he arguably does more than that by claiming that her beauty is so great that it defies description. Thus he flatters her without describing her beauty.
If those four are your options, I would have to go with C. It is the only one that makes sense.
To me, what the poem is saying is basically "you are so wonderful and beautful that I can't even manage to write a poem about or talk about you -- you're just too good for words."
If that's what he's talking about in this poem, then only C really makes sense. He's not really trying to get attention for himself so it's not A. He never claims his love is a secret so it's not B. He doesn't praise himself in the last lines so it's not D.
C kind of makes sense because he does flatter her even though he can't actually describe her.