The principle of least privilege dictates that a user should only have the minimum permissions necessary to perform their tasks. The data science team needs read-only access to a BigQuery dataset. The BigQuery Data Viewer (roles/bigquery.dataViewer) role is specifically designed for this purpose. It grants permissions to read table data and metadata but does not grant permissions to modify data, delete data, or run jobs. This makes it the most restrictive and appropriate role that fulfills the stated requirements.

A. BigQuery User (roles/bigquery.user): This role is too permissive. It allows users to run jobs (including queries) and create new datasets, which goes beyond the simple read-only requirement.

B. Project Editor (roles/editor): This is a basic role with broad permissions to create, modify, and delete most resources within a project, which violates the principle of least privilege and the explicit "no modify/delete" constraint.

D. BigQuery Data Editor (roles/bigquery.dataEditor): This role grants permissions to create, update, and delete data within tables, which is explicitly forbidden by the scenario's requirements.

1. Google Cloud Documentation, "Predefined roles and permissions for BigQuery": This document details the specific permissions for each BigQuery predefined IAM role.

Section: BigQuery Data Viewer (roles/bigquery.dataViewer): "Provides read-only access to tables and their data." This directly supports the choice of option C.

Section: BigQuery User (roles/bigquery.user): "Provides permissions to run jobs... and to create new datasets." This confirms that option A is more permissive than required.

Section: BigQuery Data Editor (roles/bigquery.dataEditor): "Provides permissions to create, update, and delete a table's data." This confirms that option D violates the requirements.

2. Google Cloud Documentation, "Basic and predefined IAM roles": This document describes the basic roles, including Editor.

Section: Editor role (roles/editor): "Grants permissions to view and modify all resources in a project." This confirms that option B is excessively permissive.