**Request: Refusal**

The word "request" implies a desire or a plea for something to be done or granted. On the other hand, "refusal" refers to the act of declining or rejecting that request. When someone makes a request, they are seeking a positive response or an affirmation, but when they receive a refusal, their request is denied or turned down.

**Trial: Failure**

In a similar vein, the relationship between "trial" and "failure" is one of opposition. A trial can be defined as a formal examination of evidence or facts in order to reach a decision or determine guilt or innocence. It is a process that aims to achieve a particular outcome, such as justice or resolution. On the other hand, "failure" refers to the lack of success or the inability to meet expectations or achieve a desired outcome. When a trial ends in failure, it means that the desired outcome was not attained, and the process did not yield the expected results.

**Eat: Obesity**

The connection between "eat" and "obesity" can be understood through cause and effect. "Eat" refers to the act of consuming food or nourishment for sustenance and energy. It is a basic human need and a biological process that is essential for survival. On the other hand, "obesity" refers to a medical condition characterized by an excess accumulation of body fat. Obesity is often caused by excessive or unhealthy eating habits, such as consuming high-calorie foods or overeating. Therefore, the act of eating can contribute to the development of obesity.

**Swim: Water**

The relationship between "swim" and "water" is one of necessity or dependence. "Swim" refers to the action of propelling oneself through water by using the limbs. It is an activity that requires the presence of water for it to be possible. Without water, swimming would not be feasible or practical. Therefore, water is an essential element or prerequisite for swimming to occur.