I think views should be the answer.
Actually the phrase "to provide security by restricting data access" tells us that we want to give restricted access to some set of users by only giving them partial DB not the entire DB access.
Indexes are ways of speeding up searches and achieving certain kind of efficiency in query running time.
Sequence is just a feature of DBMS to give unique incrementing numbers.
Eg:
CREATE SEQUENCE sequence_name
MINVALUE value
MAXVALUE value
START WITH value
INCREMENT BY value
CACHE value;