Definitions:
Due diligence is the act of investigating and understanding the risks a company faces.
Due care is the development and implementation of policies and procedures to aid in protecting the company, its assets, and its people from threats

SIEM is a combination of Security Incident Management(SIM)and Security Event Management(SEM).
A SEM system centralizes the storage and interpretation of logs and allows near real-time analysis which enables security personnel to take defensive actions more quickly. A SIM system collects data into a central repository for trend analysis and provides automated reporting for compliance and centralised reporting.

The primary issue to remember when governing cloud computing is that an organization can never outsource responsibility for governance, even when using external providers. This is always true, cloud or not, but is useful to keep in mind when navigating cloud computing's concepts of shared responsibility models Ref: CSA Security Guidelines V4.0

Explanation/Reference: