The correct option is "Length." In programming, especially when working with strings, the length operation is used to determine the number of characters or elements in the string. It's a fundamental operation for various string manipulations, such as substring extraction, comparison, and traversal. Understanding string length is essential for writing robust and efficient code when dealing with text data.

Holding a retrospective meeting is crucial in Agile methodology as it promotes continuous improvement. By identifying and addressing the root causes of interruptions, the team can implement strategies to minimize them in future sprints, thus maintaining Agile principles of adaptability and self-organization.

The main goal of a Distributed Denial of Service (DDoS) attack is to overwhelm a target server or network with a flood of traffic, rendering it unavailable to legitimate users. This is achieved by coordinating multiple compromised devices, often referred to as a botnet, to send an excessive amount of requests or data to the target, leading to a denial of service for legitimate users.

Kanban and Scrum are both Agile methodologies but differ in key aspects. Kanban focuses on flow and limiting work in progress, allowing teams to visualize and optimize their processes continuously. On the other hand, Scrum employs fixed-length iterations called sprints, defined roles like Scrum Master and Product Owner, and timeboxes for meetings and activities. Understanding these differences is crucial for choosing the right approach for a project.

Polymorphism is a fundamental concept in OOP that allows objects to be treated as instances of their parent class, even when they are instances of their child classes. This facilitates code reusability and flexibility. An example of polymorphism is method overloading or overriding, where different classes may have methods with the same name but different implementations.

The correct option is "let." In JavaScript, the "let" keyword is used to declare variables that are block-scoped, meaning they are limited to the block in which they are defined. This is different from the "var" keyword, which declares variables with function scope or global scope. "const" is used to declare constants, and "block" is not a valid keyword for variable declaration in JavaScript.

To remove sensitive information from the Git history without affecting the current state of the project, you can use git filter-branch. This command helps rewrite the repository's history by filtering out the specified sensitive files or commits. After filtering the history, force-push the changes to update the remote repository. It's essential to communicate with the team about this action to ensure everyone is aware of the changes made to the repository's history.

The DELETE statement in SQL is used to remove one or more rows from a table based on specified conditions. When you execute a DELETE statement, you can use the WHERE clause to specify which rows to delete. If you omit the WHERE clause, all rows in the table will be deleted, which should be done with caution as it can lead to data loss. Unlike TRUNCATE, DELETE is a DML (Data Manipulation Language) statement that generates transaction logs and can be rolled back if necessary. Understanding how to use DELETE safely and effectively is important for managing data in SQL databases.

The correct option is Spiral. The Spiral model is known for its risk-driven approach to software development. It involves iterative cycles of planning, risk analysis, development, and evaluation, allowing teams to address potential risks early in the project lifecycle. By incorporating risk management practices, the Spiral model aims to minimize project uncertainties and improve the overall project success rate. This model is particularly suited for complex projects where risks need to be carefully managed throughout the development process.

The "git merge" command combines changes from different branches into one. It's commonly used to integrate changes from a feature branch back into the main branch, ensuring a smooth and consolidated codebase without losing any work.