Q: React is mainly for building _____________.

Answer: A

Explanation:

React is mainly for building User interfaces.

Faster and better, thanks to Virtual DOM.
Can be used on both Client side and server side. - If your app is more of dynamic data, you can go with client side scripting where you need not request the DOM for every change. - Static page can be rendered using server side scripts. - A good mixture of both helps maintain the page safe and efficient.
Helps to maintain the readability of apps using components which is discussed later. - Can easily update the state by refering the components.