Upgrade the App Service plan to a larger pricing tier which provides extra CPU memory disk and premium features is correct.

Upgrading the App Service plan to a larger pricing tier which provides extra CPU memory disk and premium features is vertical scaling because it increases the resources available to the same application instance or instances rather than increasing the number of copies. Vertical scaling adds more vCPU and memory and can provide larger disk and premium platform features so the app can handle heavier workloads on each instance.

Increase the number of instances of the web application so additional copies run concurrently is incorrect because that describes horizontal scaling. Scaling out adds more instances to run concurrently and distribute load rather than increasing CPU memory or disk for each instance.

Deploy another instance of the app in a different region to improve latency for remote users is incorrect because deploying to another region is about geo distribution and reducing latency for remote users. That approach creates additional geographically separated instances and is not the same as increasing the size of an instance.

Use Cloud Load Balancing to distribute traffic across endpoints is incorrect because load balancing distributes traffic across multiple endpoints and supports horizontal scaling and fault tolerance. It does not increase the CPU memory or disk of an existing App Service instance so it does not represent vertical scaling.

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