The correct answer is D. All of the mentioned.
OpenCPU, OpenDisk, and OpenMem are all projects that are used for calling R products from web.
OpenCPU is a web-based platform that allows users to run R code in the cloud. It provides a simple interface for creating and running R scripts, and it can be used to access data from a variety of sources.
OpenDisk is a project that provides a way to store and access R data in the cloud. It offers a number of features that make it easy to manage data, including the ability to create and manage folders, upload and download files, and share data with others.
OpenMem is a project that provides a way to run R code in the cloud without having to install R on your own computer. It offers a number of features that make it easy to use, including the ability to create and manage R environments, run R scripts, and share R code with others.
These projects are all useful for different purposes, and they can be used together to create a powerful R environment that can be accessed from anywhere.