Fill in the Blanks

'Set out to' is the proverbial use. Hence, the answer.

Past perfect: Had + V3.  Hence, Option 3 is the correct answer.

The sentence is in past continuous tense. Hence, option 2 is the correct answer.

For making request, we use 'could' and for polite refusal we use 'can't.' Hence, option 3 is the correct answer.

'Would' is used to ask something politely and 'cutting back (on something)' is the correct phrase, which means 'to reduce the use'. Hence, option 1 is the correct answer. 

'Must' is used to show certainty. Hence, option 1 is the correct answer.

It is the correct sequence.

'A little' is used with non-count words. 'Little' means 'almost nothing' but we need a positive word to fit in the context here. Hence, option 1 is the correct answer.

'Few' means 'hardly any or none' which is correct usage in this context. Hence, option 2 is the correct answer.

The sentence is trying to say water contains impure things, so it's contaminated. 'Contaminated' water has 'adverse' impact on our health. Hence, option 3 is the correct answer.

'Much' is used to quantify (calculate the amount of) non-countable items. Hence, option 1 is the correct answer.

 As computer stores data; 'wardrobe' is used to store clothes. Hence, option 4 is the correct answer.

As butter is made from milk; 'juice' is made from fruits. Hence, option 3 is the correct answer.

According to the sentence his father 'wanted' to send him abroad. Thereafter, sentence is joined with conjunction 'But' which shows a contradiction, hence, 'refused'. Option 3 is the correct answer.

Gap 18 connects "This was" with "it was only under the powerful rays of the sun". This is a cause-effect relationship explaining WHY the cotton plant was called 'Daughter of the Sun'. "Because" correctly introduces the reason. "Although" shows contrast, "for" is a conjunction, and "why" doesn't grammatically fit.