Fill in the Blanks

Ensure means to make certain that something will occur. Insure refers to financial protection, and assure refers to removing someone's doubts.

Piteous describes something that inspires pity or compassion, which fits the context of the orphans. Pitiful is often used to describe something inadequate or contemptible, while pitiable is a synonym for piteous but less common in this specific collocation.

Intensive application refers to concentrated or thorough effort, which is the standard collocation for academic study. Intense refers to the strength of a feeling or quality, not the manner of application.

Income is the general term for money received, especially on a regular basis for work. Remuneration is formal and usually refers to payment for specific services, while earnings often refer specifically to wages.

An allusion is an indirect or passing reference to something. Illusion refers to a false perception, and delusion refers to a false belief.

The sentence asks about satisfying one's needs or wants through extra work. 'Wants' is the most idiomatic term in this context for things one desires to acquire.

The phrase 'slow in understanding' is the correct idiomatic construction to contrast with 'intelligent'. Other options are grammatically awkward or redundant in this context.

The sentence describes a future consequence of a past event. 'Will not go' is the correct future tense form to express a firm decision based on the principal's behavior.

In the context of widespread unemployment, 'temporary' work is the most logical term to describe the type of work that is hard to find. 'Casual' is also a type of work, but 'temporary' fits the flow of the sentence better in standard usage.

The phrasal verb 'lay off' means to discharge a worker, typically temporarily or permanently, due to a shortage of work. This fits perfectly with the context of a discontinued shift.

'Rolling in wealth' is an idiomatic usage. It means 'to be extremely rich; to enjoy the benefits or luxuries of great wealth'.  

'Smack of' means to give an indication of something; be suggestive of something. It fits the context here.  

'Derogatory' means 'insulting' and 'derogatory to' means that the remarks work to tarnish the person's reputation.  

The word until is used in the context of time and roughly means before and up to the time. Unless refers to a precondition for something else to be. Here, the sentence implies 'till the time you don't complete your work...'. So, option 3 is the correct answer.

While means during the time (they were playing). So, it is the correct conjunction here.