'Improve' is the best replacement for 'ameliorate', as both words convey the idea of making conditions better.

In the context of the passage, 'mitigate' means to reduce the severity of an issue, making 'reduce' the best replacement.

'Ubiquitous' means present everywhere or widespread, so 'common' is the best replacement in this context.

'Common' is the best replacement for 'ubiquitous', as it conveys the idea of smartphones being widely present in society.

Sad is the only word that conveys a negative emotion, while the others are positive.

Carrot is a vegetable, while the others are fruits.

Teacher is the only profession that is primarily educational, while the others are in the medical field.

Slow is the only word that indicates a lack of speed, while the others indicate speed.

Gloomy is the only word that conveys a negative emotion, while the others are positive.

Timid is an antonym of the other three words.

Learn is the only action that involves receiving knowledge, while the others involve giving knowledge.

'Arduous' means difficult, making option 2 the closest in meaning.

The word 'meticulous' means showing great attention to detail, which is closest in meaning to 'thorough'.

In the context of the passage, 'mitigate' means to reduce the severity of an issue, making 'reduce' the closest synonym.

'Ubiquitous' means present everywhere or widespread, making 'widespread' the closest synonym in meaning.

'Flower' is a homophone for 'flour', sounding the same but having different meanings.

'Happiness' is a noun, while the others are not.

'Under' is the preposition in the sentence.

'Under' is the preposition that shows the relationship between the cat and the table.

'Benevolent' refers to being kind and well-meaning. Hence, the synonym is 'kind'.

'Candid' means truthful and straightforward; thus, it is synonymous with 'honest'.

'Challenging' is a synonym for 'difficult', indicating something that requires effort to overcome.

'Diligent' means having or showing care and conscientiousness in one's work or duties.

'Frugal' means sparing or economical with regard to money or food.

'Hasty' means done with excessive speed; quick.

'Meticulous' means showing great attention to detail, which is synonymous with 'thorough'.

'Guide' is a synonym for 'navigate'.

'Vigilant' means keeping careful watch for possible danger or difficulties.

'Vivid' means producing powerful feelings or strong, clear images in the mind, which is synonymous with 'bright'.

'Ephemeral' means lasting for a very short time, similar to 'transitory'.