An employees collection contains documents with fields such as _id, name, age, department, and salary.

The first argument to find() is the query filter and the second argument is the projection. Because the requirement applies to every employee, the filter must be an empty document {}. The projection must include name and age while explicitly suppressing _id. MongoDB includes _id by default even in inclusion projections, so { name: 1, age: 1 } would return three fields: _id, name, and age. Adding _id: 0 is the documented exception that allows _id to be excluded from an otherwise inclusion-style projection. Option C therefore produces exactly the requested fields. Options A and B mistakenly place projection-like expressions in the filter position, which would cause MongoDB to search for documents where those fields literally match the specified values rather than controlling returned fields. Option D is close but violates the word “ONLY” because _id remains present. Projection design can also reduce network traffic and, when a suitable index covers both the predicate and projected fields, can contribute to covered-query plans. For this requirement, however, the essential syntax is find({}, {name:1, age:1, _id:0}), so C is correct.

Study Guide reference/topic:MongoDB Architecture and Core Operations - find(), filters, projections, inclusion fields, and _id exclusion.

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