In the scenario described, the project involves developing a system to control traffic lights at busy road junctions, focusing on safety-critical operations but deemed low-risk due to the team's high level of expertise.

Option B (4), characterized by ♦ (recommended) for Test Automation and ♦+ (highly recommended) for Exploratory Testing (manual) with ♦ (recommended) for Black-box Testing, is the most fitting for this project because:

Test Automation (Recommended): For a system managing traffic lights, automated tests can efficiently handle repetitive testing of scenarios involving various traffic densities and flow rates, ensuring consistent and thorough checking of system responses under controlled conditions.

Exploratory Testing (Highly Recommended): Given the critical nature of the system, exploratory testing allows testers to creatively challenge the system beyond pre-defined test cases, identifying potential real-world issues that might not be evident in scripted testing. This is particularly vital in safety-critical systems where unexpected behavior could have severe consequences.

Black-box Testing (Recommended): Black-box testing will ensure that the system meets its external specifications and behaves correctly as perceived from the outside, without the testers needing to know the internal workings. This is essential for verifying that the system's functionality aligns with its intended use in real-world traffic scenarios.

This approach, combining thorough automation with exploratory insights and specification-based validation, supports the project's safety-critical nature while leveraging the team’s expertise to manage the identified low risk .