Let’s first learn the meaning of the words:

Substitution = the action of replacing someone or something with another person or thing.

Switch = change the position, direction, or focus of.

Conversion = the process of changing or causing something to change from one form to another.

Change = an act or process through which something becomes different.

The sleep cycle is interrupted when we change the routine time of our sleep. Hence, option A is the best fit for the blank.

Note: We don’t convert our routine. We only change it.

Let’s understand the meaning of the given words:

Recuperating: Restore to good health or strength

Hurting: Give trouble or pain to

Deteriorating: Become worse or disintegrate

Hence, option B is the correct answer.

The blank needs an adverb to modify the verb ‘awaiting’. Out of all the options, ‘efficiently’ and ‘anxiously’ are adverbs, ‘flabbergasted’ is a verb and ‘bewildering’ is an adjective.

The sentence implies that the old woman was eagerly waiting for her relatives.

‘Anxiously’ meaning ‘in a way that shows you are eager to get or do something’ is the apt word for the blank.

Hence, option B is the correct answer.

The phrase “no sooner…than” is used to indicate that two events happened simultaneously or in quick succession.

Therefore, ‘no sooner’ must be placed in the blank to form a grammatically correct sentence. “Hardly”, “Scarcely” and “Barely” are conjugated with “than”.

Hence, option C is the correct answer.

The question tag uses the same verb as the main part of the sentence. If this is an auxiliary verb (‘have’, ‘be’), the question tag is made with the auxiliary verb.

Also, if the main part of the sentence is positive, the question tag is negative.

In the given sentence, the auxiliary verb is ‘have’, therefore, the question tag should be made up of ‘have’ and it should be negative too.

Hence, option D i.e. ‘have not’ is the correct answer.

“Eradication” means “the complete destruction of something” and this word is generally associated with global problems and Malaria is one of them. Therefore it should come with Malaria in the blank. Hence option A is correct.

Let’s understand the meaning of the given words:-

Chain = series of things

Check = examine

Challenge = test

Choice = selection

Here a challenged is being posed. Thus, it is the most suited one.

Hence option C is the correct answer.

 The meaning of the words given in the question are-

Seemly- as per the acceptable behavioural norms

Praiseworthy- which is worthy of admiration

Scandalous- something which causes public outrage, being offensive against morality/law.

The correct answer is option B, which only makes the sentence meaningful.

Let’s first learn the meaning of the words:

Synchronized: adjust (a clock or watch) to show the same time as another.

Assessed: evaluate or estimate the nature, ability, or quality of.

Exchanged: give something and receive something of the same kind in return.

Restored: bring back or re-establish (a previous right, practice, or situation).

The soldiers adjusted their watch to match their timings. Hence, option D is the correct answer.

Let’s first learn the meaning of the words:

Investor: a person or organization that puts money into financial schemes, property, etc. with the expectation of achieving a profit.

Invigilator: someone who is appointed by the examination board and services for maintaining the proper conduct of a particular examination in accordance with the exam regulations.

Aviator: a pilot.

Inspector: an official employed to ensure that official regulations are obeyed, especially in public services.

Hence, option (B) is the correct choice.