Usando um índice de cobertura

Question

A tabela actor tem um índice idx_actor_last_name na coluna last_name. Qual das seguintes consultas pode usar esse índice como índice de cobertura?

Answer 1

select last_name, last_update from actor order by last_name desc;

Answer 2

select last_name from actor order by last_update;

Answer 3

select distinct last_name from actor;

Answer 4

select last_name, count(*) from actor group by last_name;