Explanation

Several words are sometimes used as adverbs or sometimes used as prepositions.

A word is a preposition when it governs a noun or a pronoun, It is an adverb when it does not.

Don’t run around.  “Around” is an adverb here

Don’t loiter around the street. “Around” is a preposition here

Do you want to come in? “In” is an adverb here

Is he in his room? “In” is a preposition here

Explanation

Tell is generally followed by article A.

Explanation

Explanation

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

Explanation

I had my lunch an hour ago is a correct sentence because had working as verb here.

We should use past indefinite tense for a point of time.

Explanation

Assembling means together.

Provide + with is the  correct formation.

Explanation

 use to as a preposition to indicate a destination or direction: We're going to Liverpool next week.

Explanation

In & Within

In = completion of time

Within = Before the completion of time

I will complete this project in a week میں ایک ہفتے میں یہ پروجیکٹ مکمل کروںگا

I will complete this project within a week. 

Both sentences are correct

Explanation

Validate جائز ثابت کرنا

Disprove غلط ثابت کرنا

Explanation

The comma is used to separate short co-ordinate clauses of a compound sentence. 

It helps to link related independent clauses for better readability.

For example, “ She came, she stooped, she conquered.”