The correct answer here is "C"
Reasoning is because "Rockefeller Center" and "Empire State Building" are properly capitalized, and has a comma right after Rockefeller Center to show a pause in the sentence
1. They help you come to the answer by showing you the process
2. There are some
3. You usually come to your tutors with questions
There are many factors that could hamper an effective communication. Some of those could be: social status (if you are talking to someone who has a more important status than yourself, it may happen that they are not interested in a communication with you), use of language (if you use inappropriate words, the conversation is not going to be successful), knowledge about the subject (if you don't know what you are talking about, the conversation is likely not going to continue), atmosphere/noise, cultural differences, disabilities, etc.