In "A Defence of Poetry,” Shelley suggests that emotions experienced in life are constantly changing. Which lines from "Mutability” can also be seen as a reflection of this idea? Streaking the darkness radiantly!—yet soon
Night closes round, and they are lost for ever
We rest.—A dream has power to poison sleep;
We rise.—One wandering thought pollutes the day
We feel, conceive or reason, laugh or weep;
Embrace fond woe, or cast our cares away
Man’s yesterday may ne’er be like his morrow;
Nought may endure but Mutability.

I've found this question online. The options are every two lines:

A. Streaking the darkness radiantly!—yet soon

Night closes round, and they are lost for ever

B. We rest.—A dream has power to poison sleep;

We rise.—One wandering thought pollutes the day

C. We feel, conceive or reason, laugh or weep;

Embrace fond woe, or cast our cares away

D. Man’s yesterday may ne’er be like his morrow;

Nought may endure but Mutability.

The lines that can also be seen as a reflection of the idea that emotions experienced in life are constantly changing are:

C. We feel, conceive or reason, laugh or weep;

Embrace fond woe, or cast our cares away

Explanation:

We feel, conceive or reason, laugh or weep;

Embrace fond woe, or cast our cares away

The speaker of "Mutability", in the lines above, describes how changeable our feelings are in life. We go from happiness to sorrow, from feeling to reasoning. We forgive those who have offended us, and what once made us worry now does not matter any longer. That is, in fact, the main theme of the poem, by author Percy Shelley. There is nothing constant in life but change. Change is the only thing we can be sure of. The rest, even ourselves, is fickle, temporary.