Which of the following is a core function of Google Classroom for teachers?

The core function of Google Classroom for teachers is to collect and organize assignments. This tool is designed to streamline the assignment process, allowing teachers to create, distribute, collect, and manage student assignments all in one place. With features such as the ability to categorize work by topics, set due dates, and provide feedback directly within the platform, Google Classroom simplifies the workflow for educators.

The other options do not accurately represent the primary functions of Google Classroom. Unlimited storage is not specifically a core function of Google Classroom, as it relies on Google Drive for storage space limitations. Grading assignments is certainly a feature of Google Classroom, but it is part of the broader process of collecting and organizing assignments, thus not a standalone core function. Tracking student attendance is not integrated into Google Classroom as one of its main features, focusing instead on assignment management and communication between teachers and students.