Rule: Political/Economic Vocabulary. A government order to stop trade with another country, especially for political reasons, is called an embargo. 'Embargo' is an official ban on trade or other commercial activity with a particular country. This is the correct term. Options (a) 'incentive', (c) 'allowance', and (d) 'subsidy' are all forms of financial help or encouragement, not restrictions.

Rule: Vocabulary of Argumentation. The sentence is describing the general meaning or gist of the argument. 'Tenor' means the general meaning, sense, or content of something. It is the perfect word to describe the overall thrust of his argument. Options (a) 'digression', (c) 'distraction', and (d) 'ornamentation' (unnecessary details) are all peripheral to the main point.

Rule: Vocabulary of Lifestyles. A person who 'shuns society' and lives a 'solitary life' is a recluse. 'Recluse' is a person who lives a solitary life and tends to avoid other people. This word perfectly fits the description. Options (a) 'socialite', (b) 'extrovert', and (d) 'celebrity' are all people who are typically very involved with society.

Rule: Geographical Vocabulary. A fertile delta is formed where rivers meet and deposit sediment. 'Confluence' is the junction of two rivers, especially rivers of approximately equal width. This is the precise geographical term. Options (a) 'divergence', (b) 'separation', and (d) 'bifurcation' (division into two branches) are all words for rivers splitting apart, not joining.

Rule: Vocabulary of Deception. Promises that one has 'no intention of keeping' are misleading and false, even if they sound good. 'Specious' means superficially plausible, but actually wrong. It perfectly describes promises that sound attractive but are ultimately baseless. Options (a) 'sincere', (b) 'concrete', and (d) 'binding' are all words for real, genuine promises.

Rule: Logical Inference. For ruins to be 'revealed', the thing covering them must have been removed or pulled back. 'Receding' means to go or move back or further away from a previous position. The receding of the rainforest (due to deforestation or climate change) would logically reveal what was underneath. Option (a) 'canopy' is a part of the forest. Options (c) 'growth' and (d) 'expansion' would hide the ruins, not reveal them.

Rule: Legal/Formal Vocabulary. The detailed conditions or requirements of a formal agreement are called stipulations. 'Stipulations' are conditions or requirements that are specified or demanded as part of an agreement. The fact they were 'complex and required careful study' points to this formal term. Options (a) 'summaries', (b) 'outlines', and (d) 'generalities' all refer to less detailed aspects of the agreement.

Rule: Vocabulary of Personality. A child who is 'always asking questions and exploring' is curious and eager for knowledge. 'Inquisitive' means having or showing an interest in learning things; curious. This word perfectly describes the child. Options (a) 'apathetic', (b) 'lethargic', and (d) 'indifferent' are all words for a lack of interest or energy.

Rule: Vocabulary of Literature. A book that is a collection of writings (in this case, essays) is often called a compendium. 'Compendium' is a collection of concise but detailed information about a particular subject. It fits the description of a collection of essays. Options (b) 'novel', (c) 'poem', and (d) 'play' are different literary forms and are not collections of essays.

Rule: Vocabulary of Amount. A 'growing problem' concerning a vital resource like fresh water would be a lack of it. 'Scarcity' means the state of being scarce or in short supply; shortage. This word accurately describes the problem. Options (a) 'abundance', (b) 'surplus', and (d) 'plethora' (an excess) are all antonyms, meaning there is more than enough.