When creating an ECS instance in your Alibaba Cloud VPC, you must specify a VSwitch for that instance at the same time. Otherwise, you will not be able to create this ECS instance. This is true according to the Alibaba Cloud documentation on ECS1. A VSwitch is a basic network device of a VPC and is used to connect different cloud product instances deployed in a VPC2. A VSwitch defines a network segment within a VPC and allows you to specify the IP address range, network mask, and gateway for the network segment2. When you create an ECS instance, you must select a VSwitch that belongs to the same zone as the ECS instance3. If you do not specify a VSwitch, the ECS instance will not be able to communicate with other cloud product instances in the VPC or access the Internet. References: 1: Create an instance by using the provided wizard - Elastic Compute Service - Alibaba Cloud Documentation Center 2: What is a VSwitch? - Virtual Private Cloud - Alibaba Cloud Documentation Center 3: Create an instance by using the advanced wizard - Elastic Compute Service - Alibaba Cloud Documentation Center : [VPC FAQ - Virtual Private Cloud - Alibaba Cloud Documentation Center]

In Alibaba Cloud, resizing the system disk of an ECS instance requires stopping the instance temporarily.
This ensures data integrity and successful resizing. Once the system disk is resized, the instance can be restarted to reflect the new disk size.

Explanation
PPPoE stands for Point-to-Point Protocol over Ethernet, which is a network protocol that encapsulates PPP frames in Ethernet frames and allows multiple computers to share a single Internet connection. PPPoE is typically used by Internet service providers (ISPs) to provide broadband access to their customers, such as DSL or cable modem. PPPoE is not a protocol that is commonly supported by Open API for cloud computing service providers, because it is not designed for web-based communication and requires a dedicated connection between the client and the server. Open API, on the other hand, is a term that refers to a set of publicly available application programming interfaces (APIs) that allow developers to access the functionality and data of cloud computing service providers. Open API usually follows standard protocols that are widely used on the web, such as HTTP, Restful, and Web Service. HTTP stands for Hypertext Transfer Protocol, which is the foundation of data communication on the web. HTTP defines how messages are formatted and transmitted, and what actions web servers and browsers should take in response to various commands. HTTP is a stateless protocol, which means that each request is independent and does not depend on any previous requests or responses. Restful stands for Representational State Transfer, which is an architectural style for designing web services that are based on the concept of resources. Restful web services use HTTP methods (such as GET, POST, PUT, and DELETE) to perform operations on resources, and use standard formats (such as JSON or XML) to exchange data. Restful web services are stateless, scalable, and cacheable, and aim to provide a uniform interface for interacting with different types of resources. Web Service is a generic term that refers to any software service that is available over the web and uses a standardized format for communication, such as SOAP or REST. Web Service allows different applications to communicate and exchange data across different platforms and languages. Web Service can be described using a specification language, such as WSDL or OpenAPI, which defines the structure, operations, and parameters of the service. Web Service can also be registered and discovered using a directory service, such as UDDI or Swagger.

Explanation
The statement A is not correct, because self-built databases do not support quick deployment and elastic scaling. On the contrary, self-built databases require hardware procurement, data center hosting, and machine deployment, which can be time consuming and costly. Moreover, self-built databases have low resource utilization, as they have to accommodate peak traffic requirements, while RDS can scale elastically according to the actual demand. References: = ApsaraDB for RDS vs. Self-built Databases - Alibaba Cloud