Let's first see the meanings of the given words:

Concrete = solid or firm.

Convenient = suited to one’s comfort.

Considerate = thoughtful.

Controversial = causing public discussion and disagreement

• Out of all the alternatives, only the word "controversial" fits in the context.
   
• The suggestion was not acceptable as it was contentious or disputable. It could generate problems in the long run. 

Option B has the grammatically incorrect part.

• The error is in the use of the adverb “crucially”.
   
• We need an adjective to describe the noun “phase”. But we have used an adverb in its place in the sentence given.
   
• Thus, replace the adverb “crucially” with its adjective form “crucial” to make the sentence grammatically sound.

Thus, the correct sentence will be: The world is at a crucial phase in its fight against the virus.

The idiom “throw a spanner into the works” means to do something that prevents a plan or activity from succeeding.

e.g. We were ready to start the project when the bank threw a spanner in the works by denying the loan.

The word "sabotage" means to intentionally prevent the success of a plan or action.

Let’s first see the meanings of the given words:

Perpetuate = to cause something to exist for a long time.
e.g. He perpetuates the myth that his house is haunted.

Prevent = to stop something from happening.

Cease = to stop.

Release = to set free.

Preserve = to keep something as it is
e.g. We want to preserve the character of the town while improving the facilities.

Let’s first see the meanings of the given words:

Demean = to cause someone to become less respected.
e.g. I wouldn't demean myself by asking my parents for money.

Debase = to reduce the quality.

Belittle = to put down.

Ignore = to intentionally not listen or give attention to

Admire = to respect and approve of someone or their behaviour
e.g. I really admire people who can work in such difficult conditions.

Let’s first see the meanings of the given words:

Adept = Skilful in doing a task.
e.g. She's very adept at dealing with the media.

Inept = having or showing no skill.
e.g. He was always rather inept at sport.

Expert = having deep knowledge and skills in a particular area.

Proficient = having great knowledge and experience in a particular area.

Deft = demonstrating skill and cleverness.

The underlined part is grammatically incorrect.

• After the preposition "for", we need an objective pronoun.
   
• In the underlined part, the subjective pronoun "I" has been given.
   
• Thus, replace "I" with "me" to make the sentence grammatically sound.
   
• Also, before the noun "sister", we need the possessive adjective "my" and not the possessive pronoun "mine".

Thus, the correct sentence will be: My grandfather bought shoes for my sister and me, but he did not buy one for himself

Admirer = a person who has particular regard for someone or something.

Aristocrat = a member of the aristocracy.

Ascetic = a person who follows an ascetic life.

Connoisseur = a person who knows a lot about and enjoys one of the arts, or food, drink, etc.

The given sentence is in the active voice. It is an imperative sentence which suggests an order. 

The passive voice of imperative sentences can be made in two ways:

Active: Verb + object

Passive: 1) Let + object + be + past participle

2) You are requested/ordered/suggested + to + verb (Ist form) + object

Thus, the passive voice of the given sentence will be: Let the television be switched off.

The idiom "to drink like a fish" means to consume large amounts of alcoholic beverages.

e.g. Jeff reallydrank like a fish at the party on Saturday.