The context implies that better sleep leads to better cognitive performance, which is a 'positive' outcome.

The phrase 'early intervention' typically implies positive long-term effects, making option 2 the most appropriate completion.

Groundbreaking findings typically challenge or contradict existing theories rather than reinforce or validate them.

The word 'innovative' indicates that the findings offer fresh insights, contrasting with the other options.

The term 'tentative' implies that the findings are not yet fully confirmed, which is appropriate in a research context.

The term 'preliminary' indicates that the findings are initial and not yet final, requiring more research.

The context suggests that the argument is strong and persuasive, making 'compelling' the best choice.

The word 'interdisciplinary' indicates a broad and inclusive approach, which is beneficial for tackling complex problems.

The word 'innovative' indicates that the methodology was new and effective, deserving of praise.

The word 'enthusiasm' indicates a positive reception of the findings, which is likely to encourage further research.

Challenging long-held beliefs typically leads to skepticism rather than applause or enthusiasm.

The word 'skepticism' indicates doubt or disbelief, which is a common reaction to new scientific findings.

The word 'influenced' fits well, indicating that behavior is shaped by various factors beyond instinct.

The term 'pioneering' suggests that the research was innovative and influential, which aligns with the context of it becoming accepted in the field.

The phrase 'groundbreaking research' implies that it led to new opportunities, making option 2 the most appropriate completion.

The phrase 'met with skepticism' implies that the research questioned existing beliefs, making 'challenged' the right answer.

The context indicates that the theory gained acceptance, which aligns with credibility rather than doubt or rejection.

The word 'optimism' suggests a positive outlook, which aligns with the context of a captivating speech.

An engaging presentation typically requires an enthusiastic and dynamic tone, making option 1 the best fit.

The combination of humor and sadness suggests a 'bittersweet' tone.

Frustration typically aligns with sarcasm, making 'sarcastic' the most fitting option.

The word 'enthusiastic' describes a lively and engaging tone, which would indeed captivate an audience.

The context suggests a holistic benefit of exercise, making option 1 the most logical completion.

The conclusion drawn from the study suggests a positive relationship between physical activity and academic performance, supporting option 1.

The word 'resistance' indicates that the employees opposed the change, which fits the context of feeling blindsided.

The word 'unforeseen' suggests that the factors were unexpected, which aligns with the context of the price increase.

An increase in technology use typically transforms perceptions rather than regresses or stagnates them.

The sum of the first n terms of a harmonic progression can be expressed as 2n/(a+b) where a and b are the first two terms.

An innovative approach to problem-solving is typically flexible rather than rigid or traditional.

'Ameliorate' means to make something better or improve it, thus 'to improve' is the correct answer.