The atmospheric conditions at a certain place in a certain time are known as the weather, while the climate is the average of the weather in a place over a long period of time.
For example, talking about weather means talking about the temperature, humidity, rainfall, and wind on a given day; while climate refers to a description of the trend that these factors have during the year, such as how are their winters and what can you expect from the weather in a certain time of year.
This means the answer is D. The short-term conditions in Earth’s atmosphere at a certain time and place is the definition of the weather