Questions

Later in 1840, Rowland Hill invented the stamp, which was paid for by the sender, not the receiver.

The path that data takes from source to destination is called a Channel. A channel is a communication medium. A channel has a certain capacity for transmitting information. 

The "capacity" of a channel is the theoretical upper-limit to the bit rate over a given channel that will result in negligible errors. Channel capacity is often measured by its Bandwidth in Hz or its data rate in bits per second.

1. Lichens are plants that grow in exposed places such as rocks or tree bark.

2.  Lichens are widely used as environmental indicators or bio-indicators. They can be used as air pollution indicators, especially of the concentration of sulfur-di-oxide in the atmosphere.  

3. They need to be very good at absorbing water and nutrients to grow there.