Read the excerpt from act iii, scene ii of romeo and juliet. juliet: and bring in cloudy night immediately. spread thy close curtain, love-performing night! that runaway's eyes may wink, and romeo leap to these arms, untalked of and unseen! which words and phrases from the passage support the motif of darkness

cloudy night, unseen, and spread thy close curtain are all both phrases that support the motif of darkness. 

A cloudy night means that all of the stars should be covered. When this occurs, it means that the sky is going to be even darker now considering the fact that all sources of light are going to now be covered. Being unseen also supports the idea that it may be too dark out for anybody to see Romeo come to meet up with her, additionally supporting the fact that there was a dark enough setting that Romeo was able to navigate easily in without worry of guards catching sight of him. Spreading thy close curtain directly relates to the darkness and how Juliet is waiting for curtains to come and cover up the sky.

An additional bonus phrase could also potentially be runaway's eyes may wink. Runaway is Juliet's term for the night, although she also considers the stars to be eyes and for them to be blinking. 

I cannot be 100% with this, but I have explained each potential answer. If I am wrong, I would love it if someone could correct me. Thank you. 

The bell is just a signal that the set time of the end of class is passing. the teacher lets you know when it's okay to leave.