Database Administration Questions

Because a table can have only one primary key

A Temper.

Telnet uses TCP at layer 4. It uses IP at layer 3. We know that Telnet uses TCP/IP protocol, but in the question, it is asked specifically at layer 4 what is used in Telnet. So it is TCP at layer4 and IP at layer 3.

Envelope is a letter holder for one letter and in the question it mean that it holds one letter. Eye is also a word which starts and end with E but has one letter in the middle.

Friends can be either functions or other classes. The class grants friends unlimited access privileges.

* The declaration of the function should be preceded by the keyword 'friend'.
* The function definition will not use the keyword or the scope operator '::'.

Thus, a friend function is an ordinary function or a member of another class.

Class can have a public method for specific data type conversions.
for example:
class B
{
double value;
public  B(int i )
operator double()
{
return value;
}
};
B BObject;
double i = BObject; // assigning object to variable i of type double.
now conversion operator gets called to assign the value.