Explanation
Alibaba Cloud Auto Scaling service allows you to automatically adjust the number of ECS instances in a scaling group based on your business needs and scaling policies. You can set the minimum and maximum number of instances in a scaling group to limit the range of scaling actions1. When you create a scaling rule, you can specify the number of instances to be added or removed, or the expected number of instances after the scaling action2. You can also create a scheduled task to execute a scaling rule at a specified time or periodically3.
In this question, the customer sets the minimum number of instances to 6 and the maximum number of instances to 8 in the scaling group. This means that the scaling group will always have at least 6 instances and at most 8 instances. The customer also adds a scaling rule to remove 5 instances, and creates a scheduled task based on this rule. However, this scaling rule will not be executed if it violates the minimum and maximum limits of the scaling group. Therefore, when the scheduled task is activated once, the scaling group will only remove 2 instances, which is the difference between the current number of instances (8) and the minimum number of instances (6). The remaining number of instances in the scaling group will be 6, which is the correct answer. References: 1: Create a scaling group - Auto Scaling - Alibaba Cloud Documentation Center2: Create a scaling rule - Auto Scaling - Alibaba Cloud Documentation Center3: Create a scheduled task - Auto Scaling
- Alibaba Cloud Documentation Center.

Explanation
Web Application Firewall (WAF) is a cloud-based security service that protects web applications from common web attacks, such as SQL injection, cross-site scripting, and HTTP flood. WAF can also filter out malicious requests and bots, and ensure that only legitimate traffic reaches the web servers. WAF can help online shops to avoid HTTP flood attacks and ensure only genuine customers joining the event.
References:
Alibaba Cloud Web Application Firewall
ACA Cloud Computing Certification Exam Preparation Course
Alibaba Cloud Computing Exam Question 2022
After adding your website to the WAF protection list, you can enable HTTP Flood protection and select an appropriate protection mode for the website

Explanation/Reference: https://www.alibabacloud.com/support/after-sales

Explanation
You can create a custom image for ECS using data disk snapshots or system disk snapshots. A snapshot is a backup of the data on a disk at a specific point in time. You can use snapshots to create custom images, which are copies of the operating system and applications on a disk. You can use custom images to create ECS instances that have the same operating system, applications, and data as the original disk12.
You cannot create a custom image for ECS using CPU snapshots or memory snapshots. These are not valid terms in Alibaba Cloud. CPU and memory are not persistent storage devices, and they do not store the operating system and applications that are required for creating a custom image34. References: 1: Create a custom image from a snapshot - Alibaba Cloud1 2: What is a custom image? - Alibaba Cloud2 3: What is a CPU? - Alibaba Cloud3 4: What is memory? - Alibaba Cloud4