Questions

Here in this declaration public static void main string[] args, each keyword has its importance.

1. public - Here public is an access specifier which allows the main method to be accessible everywhere.

2. static - static helps the main method to get loaded without getting called by any instance/object.

3. void - void clarifies that the main method will not return any value.

4. main - It's the name of the method.

5. String[] args - Here we are defining a String array to pass arguments at the command line. args is the variable name of the String array.

A : B = (800 × 8+ 900+ 1000+ 1100+ 1200): (1600 × 8+ 1700+ 1800+ 1900+ 2000)
A : B = 53 : 101
Profit of A ⇒ 7700 ×53/154 = 2650 Rs.

Caves with pre-historic paintings and engravings 

The order of basicity for primary, secondary and tertiary amines are:

Secondary > Primary > Tertiary > NH3

* Amines are basic in nature as they have lone pair of electrons on nitrogen. Therefore, they have a strong tendency to donate this lone pair of electrons to electron acceptors.

* The stability of conjugate acids formed is dependent on the extent of H-bonding,and greater the number of H-atoms on N more stable is the conjugate acid.

* The conjugate acid of primary amine is the most stable with greater number (3) of H-bonds than > Secondary > tertiary. But primary amines are less basic than secondary as the electron density on the N atom is less and lone pair of electrons are not readily available for protonation.

* The two opposing factors i.e. the stability of conjugate acids formed and ease of availability of electrons for Protonation, balance each other in case of secondary amines and it is most basic.