Using standard alphabetical filing rules, which name is filed first: Lea Sy, Lea Syjuco, Lea Suarez, Lea Sumulong?

The correct answer is C. Lea Suarez

Indexed surname first, the filing order is SUAREZ, Lea → SUMULONG, Lea → SY, Lea → SYJUCO, Lea. The name filed first is Lea Suarez. "Su" comes before "Sy", so Suarez and Sumulong come first; "Sua" comes before "Sum". Then Sy (nothing before something) and Syjuco.