Questions

Alum is a common alum, potassium aluminum sulphate K2SO4.Al2SO43.24H2O which makes colloidally suspended impurities in water such as clay to settle down.

I would do the following if I run out of ideas for a new ad:

       - Word of mouth marketing

       - Direct marketing

       - Public opinions survey

       - Trade show/exhibition promotion etc.  

RADAR - RAdio Detection And Ranging.

A radar system consists of a transmitter producing electromagnetic waves in the radio or microwaves domain, a transmitting antenna, a receiving antenna (often the same antenna is used for transmitting and receiving) and a receiver and processor to determine properties of the objects. 

Radar is an object-detection system that uses radio waves to determine the range, angle, or velocity of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain.

Radio waves from the transmitter reflect off the object and return to the receiver, giving information about the object's location and speed.

Compressions and Rarefactions are characteristic of Longitudinal waves.

The direction of vibration of the particles is in the same plane as in which the wave is propagating. The particles vibrate back and forth, about their mean positions.

Concatenation of text means adding a word with other word. It can be done using Ampersand (&).

For example :

'Amper' & 'sand' = Ampersand 

Intel's 80386 was the first 32-bit processor, and since the company had to backward support the 8086. All the modern Intel-based processors run in the Enhanced mode, capable of switching between Real mode (just like the real 8086) and Protected mode, which is the current mode of operation.