Classical smog is a mixture of sulfur dioxide and coal smoke with fog. It is called London smog because of an incident which was took placed in 1952 which was known as the Great Smog of London.

(ii) It is indeed produced in a cold and humid climate because the components which are present are of reducing nature. And sunlight is not required as here oxidizing is not taking place.

(iii) It contains compounds of reducing nature.

(iv) Classical smog results from large amounts of coal burning in an area and is caused by a mixture of smoke and sulfur dioxide. Hence, indeed it contains smoke, fog and sulphur dioxide.

On the other hand, (i) is not true for classical smog as it doesn’t require the action of sunlight, etc.