Explanation

It was so dark that you could not see your hand.

that you could not see your hand, modifies the adjective - so dark.

Here the above-given part is an adverb clause

because it tells us 'how much dark' 'Ii' i.e. the subject in the main clause, 'was'.

Explanation

Generally no article required before seasons.

Explanation

Iran-Iraq War was a protracted armed conflict between Iran and Iraq that began on 22 September 1980 ended on 20 August 1988.

Explanation

Usually Article the is used before unique things like Sun, Earth, Moon etc.

Explanation

Article the is used with religious books.

Explanation

The dolphin is a very intelligent animal.

Article 'the' is used before particular animals. 

Explanation

I planted a tree ? in my garden last year. The tree ? has now grown big.

Note 1: Use "A" or "An" to talk about a person or thing unknown to your listener.

Note 2: Use "The" to talk about a person known to your listener.

Explanation

Tell is generally followed by article A.

Explanation

Article A is used with singular countable nouns pronounced with consonant sound.

Explanation

Usually Article the is used before unique things like Sun, Earth, Moon etc.