1. The problem asks: What area is most impacted by the low attendance of mothers of toddlers in Posyandu activities? 2. Let's analyze the options: - Effectiveness of cross-sector coordination: This depends on many factors beyond attendance, so impact is indirect. - Smooth funding of Posyandu: Funding is influenced by many factors; attendance affects service delivery more directly. - Regular monitoring of toddler growth and development: This requires mothers' presence, so low attendance directly hinders this. - Implementation of immunization by the health center: Immunization can still be done even if attendance is low, so less impact. - Availability of facilities and infrastructure: This is independent of attendance. 3. Therefore, the most directly affected area is the regular monitoring of toddler growth and development. Final answer: Pemantauan tumbuh kembang balita secara berkala (Regular monitoring of toddler growth and development) is most impacted by low attendance.