21. explain how an interlocking schedule at a puerto rico school works. why are interlocking schedules used? 22. why is it not always necessary to include a subject pronoun before the verb in spanish? 23. what is a heritage of many of the students at miami high school? explain why so many students of this heritage are at miami high school. 24. how would you write the sentence “you [formal] need to study for english class” and “you [informal] need to study for english class” in spanish? 25. how do researchers know that tiahuanaco was an advanced civilization?

1. Explain how an interlocking schedule at a Puerto Rican school works. Why are interlocking schedules used?

An interlocked calendar is exactly where the timetables cover each other, and they are utilized on the grounds that Puerto rico and other Hispanic nations have two distinct options on what times understudies can go to class so they required an approach to have both timetables without over swarming the school.

2. Why is it not always necessary to include a subject pronoun before the verb in Spanish?

The reason is that the ending of the conjugated verb "tells" the subject.
 o - yo 
s - tú 
vowel (a, e) = él, ella, Usted
 -mos = nosotros/nosotras 
-is = vosotros/vosotras 
-n = ellos, ellas, ustedes 
Above are the ending signals just for the Present Tense, as an example. 

3. What is the heritage of many of the students at Miami High School? Explain why so many students of this heritage are at Miami High School.

Miami high school is Cuban heritage. Due to its Cuban migration background.Miami schools have lots of Hispanics from immigration.Researchers know because they had advanced tools and their own dialectthe schools schedule interlock to make the day easy for students and they are short days.

4. How do researchers know that Tiahuanaco was an advanced civilization?

Scientists discovered Tiahuanaco as an advanced civilization, through archaeological excavations and artifacts implying the advanced engineering methods the civilization used during the ancient times.

What are the main think you have to do in this question i speak spanish i can .