Express each of the following queries in SQL.

a) Find the names of all buildings on campus (including both classroom buildings and department buildings). The resulting relation should have one attribute and no duplicate values for this attribute.

b) Find the ID and name of the instructor who has taught the most courses (i.e. has the most tuples in teaches).

c) For each department, list the department name and the average number of credits in courses in that department.

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student takes ID course_id sec_id semester year name dept_name tot_cred grade section advisor course id sec_id course course_id title dept_name credits semester department dept_name building budget Slid i id year building room_no time_slot_id time_slot time slot_id day start_time end_time instructor classroom building room_no capacity prereq course_id prereg_id ID name dept_name salary teaches course_id sec_id semester year