In which case is the driver's license suspended? (no existing penalty points)

Answer: ① Causing a traffic accident and receiving 40 penalty points

A license is suspended once penalty points reach 40, so 40 points from an accident leads to suspension. 30 or 20 points alone do not, and drunk driving that injures someone leads to revocation, not suspension. [Enforcement Rule of the Road Traffic Act, Appended Table 28]