Institution: SONALI BANK LTD Exam: Sonali Bank Ltd - Assistant Programmer - 26.08.2016 ||
Topic: ICT (তথ্য ও যোগাযোগ প্রযুক্তি), Subject: Computer and ICT (তথ্য ও যোগাযোগ প্রযুক্তি)

Best Answer Explained in Below-:

The correct answer to the question is A) Key. In the context of databases, a key is a set of one or more attributes (or columns) that can uniquely identify a row (or record) within a table. This uniqueness property is crucial because it allows for accurate data retrieval and ensures that no two rows in a table are indistinguishable from one another.

For example, in a student database, a student ID can serve as a key since it uniquely identifies each student. Without such keys, it would be impossible to distinguish between entries that may have the same attribute values, leading to data integrity issues.

The other options do not fit this definition. A determinant refers to an attribute that determines another attribute, but it doesn't necessarily ensure uniqueness by itself. A tuple is simply a single row in a database table, and a relation refers to a table structure itself, which includes both rows and columns. Thus, the concept of a "key" specifically addresses the need for uniqueness in identifiers, making it the best choice in this context.