2) This question helps you to understand data.

a) Write a PL/SQL query to list the number of occurrences for each PLCO_ID in the ovarian_data table.

Copy/paste or SNIP your PL/SQL code and the result tables first 10 rows. [2]

b) Choose plco_id that has the maximum occurrence and explain each column with your word using the ovarian_data_dictionary.pdf file (choose any row) [3]

c) Choose any plco_id that occurred once and explain each column with your word using the ovarian_data_dictionary.pdf file [3]

d) Why is the PLCO_ID in question b stored many times but the one in question c stored only once? [2]