Which among the following are the advantages of using indexers?

[answerhappygod]

a) To use collection of items at a large scale we make use of indexers as they utilize objects of class that represent the collection as an array
b) Indexers are also convenient as they can also make use of different types of indexers like int, string etc
c) An indexer allows an object to be indexed such as an array
d) All of the mentioned