The underlined part is grammatically incorrect.

* The use of “remove” is incorrect here.

* After the construction - “has/have + been”, we use either V3 (in the passive structure) or V-ing (in the present perfect continuous structure).

* We need a passive structure here as the subject “this heap of rubbish” is not a doer.

* Thus, use “removed” in place of “remove”.

* “6 months” is a duration. Thus, “for” will be used before it.

The correct sentence will be: This heap of rubbish has not been removed for 6 months.

Hence, option D is the correct answer.

The underlined part is grammatically incorrect.

* After the possessive adjective “her”, we need a noun.

* Thus, the use of “haired” is grammatically incorrect here.

* Use “hair” in its place.

* We will use the positive adjective “short” as there is no sense of comparison here.

The correct sentence will be: She cuts her hair short in the summer.

Hence, option A is the correct answer.

* The correct phrasal verb is “warn against”.

* It means to advise someone not to do something because it may have dangerous or unpleasant results.

E.g. Her financial adviser warned her against such a risky investment.

The correct sentence will be: The students were warned against coming late to school.

Hence, option B is the correct answer.

* We use the simple present tense to express habits, general truths, repeated actions or unchanging situations, emotions and wishes.

* But here, there is no such context.

* The person is telling here not to disturb the boy as he is in middle of doing something.

* The present continuous tense is used to denote the action that is ongoing or occuring in that current moment.

* Thus, replace the underlined part with “is preparing”.

The correct sentence will be: Don’t disturb the boy, he is preparing for his examination.

Hence, option A is the correct answer.

• With the verb “partake”, we use the preposition “of”.

• Thus, add “of” after “partake” to make the sentence grammatically sound.

The correct sentence will be: You are welcome to partake of this light refreshment.

The underlined part is grammatically correct. There is no need to improve it. 

Hence, option C is the correct answer.

The underlined part is grammatically incorrect.

• The subject compares the timing of the movie with his expectations, so we will use comparative degree.

• So, “longer” will be used instead of “long”.

• The use of the article ‘the’ with a comparative degree is erroneous; “a” will be used.

• Thus, 'a bit longer' is the most suited one.

The correct sentence should be :- The film by itself was good but a bit longer than I had expected.

Hence, option C is the correct answer.

The underlined part of the sentence is grammatically incorrect.

• Underlined part needs correction in adverb.

• “More” as an adverb is used to form comparative of most adjectives and adverb with two or more syllables.

For example:

As a photographer, shape and form were more important to him than color.

• “Most” as an adverb is used as a superlative form of adjectives to show the greatest degree of those adjectives.

For example:

Patience is one of the most important attributes in a teacher.

• In the given sentence we have to attach the greatest degree with adjective “important”. This can be done with the use of superlative form i.e. “most”. But in the underlined part, we have erroneously used an adverb “more” to form comparative degree of adjective “important”. Thus, adverb “most” should be in place of adverb “more”.

• Hence, “the most important” is the correct substitution.

Thus, the correct sentence will be:

I've realised that working hard is the most important thing for me

Hence, option D is the correct answer.

The underlined part of the sentence is grammatically correct.

Hence, option D is the correct answer.

The underlined part of the sentence is grammatically incorrect.

* The underlined part needs correction in verb.

* The first part of the sentence talks about a basket which had a dozen eggs in it (past).

* The use of the conjunction “but” shows that the situation has changed. “Now” tells us that he is talking about the current situation at hand. Thus, we will use the simple present tense in the underlined part.

* For the plural “six”, we will use “are” after “there”.

* Hence, “there are” is the correct substitution.

Thus, the correct sentence will be:

There were a dozen eggs in the basket, but now there are only six.

Hence, option B is the correct answer.