Explanation
Public clouds, such as AWS and Azure, are massive systems run by major corporations, and they account for a significant share of Internet traffic and services. They are always expanding, offer enormous resources to customers, and are the least likely to run into resource constraints compared to the other deployment models.
Private clouds would likely have the resources available for specific uses and could not be assumed to have a large pool of resources available for expansion. A community cloud would have the same issues as a private cloud, being targeted to similar organizations. A hybrid cloud, because it spans multiple clouds, would not fit the bill either, without the use of individual cloud models.

Explanation
Sensitive data exposure occurs when information is not properly secured through encryption and secure transport mechanisms; it can quickly become an easy and broad method for attackers to compromise information. Web applications must enforce strong encryption and security controls on the application side, but secure methods of communications with browsers or other clients used to access the information are also required. Security misconfiguration occurs when applications and systems are not properly configured for security, often a result of misapplied or inadequate baselines. Insecure direct object references occur when code references aspects of the infrastructure, especially internal or private systems, and an attacker can use that knowledge to glean more information about the infrastructure. Unvalidated redirects and forwards occur when an application has functions to forward users to other sites, and these functions are not properly secured to validate the data and redirect requests, thus allowing spoofing for malware or phishing attacks.