Choose the appropriate word which can be substituted for the given sentence: 'When someone is not able to sleep'.

Choose the appropriate word which can be substituted for the given sentence: The study of ancient sciences.

Choose the appropriate word which can be substituted for the given sentence: $A$ person whose age is $100$ or more than $100$ years.

Choose the appropriate word which can be substituted for the given sentence: 'One who sacrifices his life for a cause'.

Choose the appropriate word which can be substituted for the given sentence: '$A$ set of rules or code of diplomatic etiquette and precedence'.

Choose the appropriate word which can be substituted for the given sentence: $A$ person interested in collecting,studying and selling of old things.