What is the suitable file structure for database if queries are select (relational algebra) operations only?

Searches related to A relation R(A, B, C, D) has to be accessed under the query σB=10(R). Out of the following possible file structures, which one should be chosen and why? i. R is a heap file. ii. R has a clustered hash index on B. iii. R has an unclustered B+ tree index on (A, B).