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Consider the following schema, where the keys are underlined (di?erent keys are underlined di?erently):

Professor(Id, Name, Department)
Course(CrsCode, Department, CrsName)
Teaching(ProfId, CrsCode, Semester)

Consider the following query:

SELECT       C.CrsName, P.Name
FROM        Professor P, Teaching T, Course C
WHERE      T.Semester=’F1995’ AND P.Department=’CS’
                  AND P.Id = T.ProfId AND T.CrsCode=C.CrsCode

Assume the following statistical information: 1. 1000 tuples with 10 tuples per page in Professor relation 2. 20,000 tuples with 10 tuples per page in Teaching relation 3. 2000 tuples, 5 tuples per page, in Course 4. 5-page bu?er 5. 50 di?erent values for Department 6. 200 di?erent values for Semester 7. Indices Professor relation On Department: Clustered, 2-level B+ tree On Id: Unclustered, hash Course relation On CrsCode: Sorted (no index) On CrsName: Hash, unclustered Teaching relation On ProfId: Clustered, 2-level B+-tree On Semester, CrsCode: Unclustered, 2-level B+ tree a. First, show the unoptimized relational algebra expression that corresponds to the above SQL query. Then draw the corresponding fully pushed query tree. b. Find the best execution plan and its cost. Explain how you arrived at your costs.

_____ is based on combinations of the three logical structures, or control structures, which serve as building blocks for the process.

A. Modular design B. Interface design C. Visual design D. Product design