Does n number of WiFi connection can be merged in a single WiFi connection?

Basically, you are trying to merge 4 different wireless connections' bandwidth.

1. You will need four wireless adapters, if you are using laptop, buy USB wireless adapters(if using Desktop buy PCI slots NIC).

2. Install all the wireless adapters in your laptop

3. Connect each WiFi to different USB wireless adapters.

Now to merge the bandwidth of four different WiFi follow these steps:- 

4.  Go to Run - type ncpa.cpl

5. You will see a window named Network Connections and all the adapters listed.

6. Select multiple WiFi adapters  you want to merge.

7. Right click and click on Bridge Connections.

8. All the WiFi adapters will be bridged and a new adapter name Network bridge will be created.

Your bandwidth is merged and now you can use Internet at high speed (but only on single System).

If you want to distribute this merged WiFi Connection to be used by other devices. You will have to buy Load-balancing router. 

You can connect multiple routers with different wireless networks to your load-balancing router in order to process all of the routers' connections through one broadcast.

wireless Adapter correct answer.