What is the optimal and most efficient mechanism to assess the controls CSP is responsible for?

An independent contractor is assessing security maturity of a SaaS company against industry standards. The SaaS company has developed and hosted all their products using the cloud services provided by a third-party cloud service provider (CSP) .

What is the optimal and most efficient mechanism to assess the controls CSP is responsible for?
A . Review third-party audit reports.
B . Review CSP’s published questionnaires.
C . Directly audit the CS
E . Send supplier questionnaire to the CS

Answer: B

Explanation:

Reference: https://www.sapidata.sm/img/cms/CAIQ_v3-1_2020-01-13.pdf