– a large quantity of … quantity refers to bulk or mass, number to individuals or units. (e.g. a large number of cars). Number is used for countable nouns. and quantity is used for inanimate objects which can be measured.

• (that) the work be finished (or shall be finished). With words expressing command, necessity and the like either the subjunctive form is used, or a verb-phrase containing the auxiliary shall or should is substituted for it. The indicative mood should not be used.

'Spent' in place of 'spend'. The reporting verb is in the past tense and thus all other clauses must be in the past tense.

'That he had a hand.' The indefinite article ‘a’ is used before a singular noun which is countable when it is mentioned for the first time and represents no particular person or thing."Had a hand in' is an idiom meaning to be involved in something.

With countable nouns 'fewer' is to be used. 'Fewer' refers to individuals or units; less to bulk or mass. (e.g. fewer pennies, less money). There might be a is a comparision to a previous day or a previous meeting. So, a comparative form should be used.

‘had been recorded’. When two events are in succession in the past tense; the earlier event in time will take past perfect tense and the latter event will take simple past tense.

‘Which’ should be used instead of 'whom'. ‘Who’ and ‘whom’ are relative pronouns; the pronoun 'which' is used for persons' selection purposes. 

'Did you have lunch?' The names of everyday meals, which are a matter of routine, do not take any article before them.

Only perfect continuous tense can be used here.Here only option in this tense is "had been working". So, it is the correct asnwer. 

From/in. Correct preposition indicating the place is “from” and something gets lost “in” something.

With/about. Discussions are held with someone about (regarding) some matter.

so big Cause and effect relationship is stated. “So” will be followed by “that”.

is higher than any other one Since a comparison is made between two groups (Observation deck at World Trade Centre  and other ones in Delhi) so comparative degree will be used. Whenever we make a comparison between two things preposition 'than' has to be used.

(is discernible). The subject of the sentence is ‘nothing’ and not ‘fraud and double-dealing’. Nothing is treated as singular. Hence ‘is’ and not ‘are’.

'The' Narmada. Definite article is used before names of seas, rivers, chains of mountains, groups of islands and plural names of countries.

Between/since. Since the talk is between two people (you and me) so conjunction “between” will be used. For certain time onwards in this case (ten o'clock onwards) we use preposition “since”.

'should it be stored for later consumption'. 'Only' constructions are followed bt helping verb before the subject. 'should it'

To. With the word attend we use preposition “to”.

It should be ‘You look more handsome now’ or 'You look much more handsome now'. 'Now' shows that comparison is being done with an earlier  time, so we need to use 'more'.

(very much interested). With many adjectives very may be used along with others - especially with participles - very much, very well and similar combinations with very are required. It could be 'much interested' also.

'than that of inland resorts' The characteristic or quality of one object cannot be compared with another object as a whole. (The climate of Trivandrum cannot be compared with Inland resorts, but with the climate of these resorts).

 ‘Who work for others’ in place of ‘work for others’. One form of the verb pattern should be used with one subject. If the verb pattern changes the subject must be mentioned. Here, the subject is ‘those who’ and the two verb constructions are ‘who are’ (auxiliary verb) and 'who work' (action verb). Thus, there must be a subject with the second.

For/beyond. As specific time is mentioned (two weeks) so the correct preposition will be “for” and “ “beyond” is the only preposition given which indicates limit.

Correct word to be used here is 'can'. ‘Hardly’ conveys a negative meaning, and if we use it with ‘cannot’, we are making the mistake of using a double negative. So sentence is- 'I can hardly read the letter'. 'Hardly conveys that the letter can be read with difficulty/only just. If we remove hardly it will convey the meaning that the speaker cannot read the letter which changes the meaning of the sentence.

The addition of preposition “as” in options (2) and (4) make the sentence incomplete. The correct phrase is “old enough” and “not enough old”.