You have a table created as follows:
create table foo (c1 int, c2 char(30), c3 int, c4 char(10))
If column c1 is unique, which of the following indexes would optimize the statement given below?
Select distinct (c1), c3 from foo where c1=10

A.
create index foox on foo (c1)

B.
create unique index foox on foo (c1,c3)

C.
create unique index foox on foo (c1) include (c3)

D.
create index foox on foo (c1,c3)

Explanation: