In EJS (Embedded JavaScript), you use <%= %> to output data to the template and <% %> to execute JavaScript code within the template. The other options are not valid EJS syntax.

In Mocha, the beforeEach hook is used to perform setup activities before every test case within a suite. It runs before each test case. The other options (before, setup, and suiteSetup) represent different hook names or are not used for this specific purpose in Mocha.

CRUD stands for Create, Retrieve, Update, Delete. These are the four fundamental operations for managing data in a SQL database. Create adds new records, Retrieve reads data, Update modifies existing records, and Delete removes records.

The Events module in Node.js extends the 'EventEmitter' class to allow the creation of event emitter instances. This class provides the functionality for registering event listeners and emitting events.

A JavaScript file that uses the export keyword is considered a "module." Modules are used to encapsulate and export functionality that can be used in other parts of the code.

The primary purpose of the NPM (Node Package Manager) registry in Node.js development is to host and distribute Node.js packages and modules. It serves as a centralized repository for sharing and discovering reusable code, making it a crucial component of the Node.js ecosystem. Option 1 is incorrect because NPM is not used to install Node.js itself; you would use a Node.js installer for that. Option 2 is incorrect because NPM primarily manages packages on a project-specific level, not globally. Option 4 is incorrect because the NPM registry is not used to execute JavaScript code directly.

The Time-To-Live (TTL) value in caching determines how long the data should remain in the cache before being expired. When data expires, it is removed from the cache and, if needed, can be fetched again from the source.

When evolving schemas in distributed databases, it's important to apply changes sequentially with backward compatibility. This means making changes in a way that allows both old and new versions of the schema to coexist temporarily, ensuring data consistency during the transition. Applying changes simultaneously or only to a single node can lead to data inconsistencies.

In Mocha, the primary difference is that the beforeEach hook runs before each test case, ensuring a clean state for each test, while the beforeAll hook runs once before all test cases. This means that changes made in beforeEach won't persist between test cases, but changes in beforeAll will. The other options are incorrect regarding their behavior.

To ensure that your Express app is secure and defends against common web vulnerabilities, you should implement security middleware, validate user inputs to prevent injection attacks, and follow secure coding practices to mitigate risks. Regularly updating Express is also essential for security.