The use of perfect tenses of the verb is important because

Perfect verb forms also apply to past and future tenses, where an event took place before another or will be completed in the future before another action.

Explanation:

Communicating events with indiscrete times can be tricky in English. The present perfect tense is supposed to make this easier. If you want to explain an event that happened at an indefinite time in the past or that began in the past and continues into the present.

what is the sentences

the correct answer is b:

romeo and company are going to sneak in through the back.  

romeo was depressed because he wanted to try to forget about rosaline and be happy again. so mercutio told him to just go and have fun. and they sneak through the back because capuleto and montague families were enemies.