What are the dimensions of a 10-gram Pi-Ball at night?

The correct answer of 74 inches reflects the standard dimensions for a 10-gram Pi-Ball, which are specifically governed by guidelines that take into account various conditions, including visibility, air density, and operational safety at night.

When considering the use of a Pi-Ball, which is typically employed in parachute operations, its size is essential for ensuring that it provides the necessary visual reference and data for accurate drop calculations. The dimensions of 74 inches are designed to be easily visible and manage airflow optimally, particularly in low-light scenarios such as nighttime operations.

The other choices do not align with the established standards for this equipment, as 70 inches, 80 inches, and 90 inches either fall below the required visibility thresholds or exceed the dimensions needed for effective use. Therefore, the 74-inch measurement is critical for fulfilling the operational requirements effectively and safely.