ACP-Cloud1 Exam Dumps : ACP Cloud Computing Certification

RDS provides whitelist access policies. You can set permitted IP addresses and IP network segments to effectively prevent hackers from attacking the server by port scanning1. A whitelist is a list of IP addresses or CIDR blocks that are allowed to access an RDS instance. By default, the whitelist is empty, which means that no IP address can access the RDS instance. You can add IP addresses or CIDR blocks to the whitelist to allow access from specific sources. You can also modify or delete the whitelist as needed2. Whitelist access policies help improve the security of your RDS instance and protect your data from unauthorized access3. 

According to the Alibaba Cloud Elastic Compute Service documentation, if the current public bandwidth does not meet your business requirements, you can upgrade or downgrade the public bandwidth configurations without the need to reboot the ECS instance. This can improve the network performance and response speed of the ECS instance. Upgrading the CPU, memory, or disk of the ECS instance may not solve the issue of bandwidth utilization, and may require rebooting the ECS instance. References: Public bandwidth - Elastic Compute Service

Default VPCs do count toward your overall VPC quota in Alibaba Cloud, contrary to option D. Each region has a single default VPC that is automatically created by Alibaba Cloud, and users can create additional VPCs, which are then labeled as non-default VPCs. Default VPCs also have different constraints and operational characteristics compared to user-created VPCs, such as specific configurations for ease of use in basic setups.