Q.Which is gateway to internet ?

A portal is the gateway to the internet, so the correct answer is option (b) Portal.

Why this is the answer, in the context of online marketing (e-marketing):

• A web portal is a website that acts as a single point of access or entry door to a large amount of information and services on the internet. Because it opens the door to the wider web, it is described as the "gateway to the internet". Examples students see every day are search-and-service portals like Yahoo or Google.
• (a) Modem is only a hardware device that connects a computer to a telephone/broadband line; it enables the connection but is not itself the gateway a user browses through.
• (c) Webinar is a seminar or lecture conducted online, not an entry point to the internet. …