Fill in the blanks with suitable articles.

1.    The stone hit me on ——————- leg.

a)    The
b)    A
c)    No article

2.    I asked him to go to —————– post office.

The articles are not used:

1.    Before proper, material and abstract nouns used in a general sense:

London, France, Tom, gold, rice, honesty, virtue

The definite article the is used:

6.    When we refer to the imaginary geographical lines:

The Equator, The Tropic of Cancer, The Tropic of Capricorn, The Longitude, The Latitude

The definite article the is used in the following cases:

1.    When a singular noun represents a whole class.

Correct the following sentences:

The indefinite article (a/an) is used before a noun in the following cases:
a) To convey the numerical sense of one

I have a pen.
There is a cat on the roof.
A hundred kilos make a quintal.